# Jeromy Anglim's Blog: Psychology and Statistics

## Monday, December 21, 2009

### How to Write Predictions and Hypotheses in Psychological Research Reports

This post discusses the topic of predictions in psychological research. The main aim of the post is to provide assistance to researchers who are in the process of writing their predictions in a thesis, lab report, or journal article. The post: (a) provides an overview of the purpose of prediction in empirical reports; (b) discusses properties of predictions, such as the rationale, research question, and relationship with researcher belief; (c) discusses types of prediction, including abstract versus operational, qualitative versus quantitative, and single versus grouped; and (d) presents ideas about how to write about predictions in the introduction of an empirical report.

## Thursday, December 17, 2009

### Matrix Algebra in R: Resources, Videos, Textbooks

I noticed how John Myles White has posted a useful overview of Matrix Algebra in R. This post lists a couple of other resources that are available on the Internet on the topic, including R resources, online video courses, and online textbooks.

## Tuesday, December 15, 2009

### Problems with High Resolution Laptops and External Monitors

In this post I outline why buying a high resolution laptop is a bad idea if you ever plan to use an external monitor and run an extended desktop.

## Friday, December 11, 2009

### How to Write the Introduction Section in Psychology: Theses, Lab Reports, and Journal Articles

This post discusses how to write an effective introduction in a psychological empirical report, including lab reports, theses, and journal articles. It discusses: (1) the overall purpose of the introduction; (2) the different elements of the introduction, including the opening, literature review, and the current study; (3) issues associated with main and transitional introductions in multiple study investigations; and (4) provides links to additional resources on writing introductions.

## Wednesday, December 9, 2009

### Writing a Method Section in Psychology: Lab Reports, Theses, Articles

This post discusses how to write a method section in psychology. It has relevance to writing journal articles, theses, and lab reports. It includes discussion of: (a) key elements to include in each section; (b) specific issues to consider; and (c) links to online and offline resources.

### Article Deconstruction: How to Write a Method Section in Psychology

The following post applies an approach that I call article deconstruction to extract principles for writing a Method section in a psychological empirical report. The post aims to both extract useful principles for writing a Method section and to demonstrate how article deconstruction can be applied to writing challenges in scientific psychology. It builds on my other post discussing general principles and resources for writing a method.

## Tuesday, December 8, 2009

### Dark Nudges: Your Loss is the Company's Gain

I've recently been thinking about the concept of the nudge. I'm talking about ways that systems can be altered to encourage or discourage particular behaviour. As opposed to telling people that they cannot do something or that they must do something, a system is set up that just makes a given behaviour a little easier or a little harder. A classic example is the difference between opt-out versus opt-in systems for organ donors, and how an opt-out system can dramatically increase organ donor rates. However, while some writers are commenting on the beneficial effects of nudges, I've been thinking more about the dark side of the nudge. Specifically, I've been thinking about the ways that companies use nudges for their own advantage and to the detriment of the customer. This post presents a few examples of dark nudges that have recently come my way and makes some general comments about dark nudges.

## Monday, December 7, 2009

### Structural Equation Modelling and Path Analysis Resources

The following post lists some resources for conducting structural equation modelling and path analysis.

### Multinomial Logistic Regression: SPSS Resources

This posts sets out a few Internet resources on analysing and interpreting a multinomial logistic regression.

### Meta-Analysis: Tips, Resources, and Software

The following discusses issues related to conducting a meta-analysis. It sets out: (a) some tips for getting started; (b) some online resources for learning about meta-analysis; (c) some links to software for conducting meta-analysis; and (d) a few thoughts that I have had about meta-analysis.

## Wednesday, December 2, 2009

### Practice Questions for Statistics in Psychology (Undergraduate Level)

This post is intended for undergraduate students who are studying statistics in psychology. The post provides links to online resources that provide practice questions.

## Monday, November 23, 2009

### Memory Management in R: A Few Tips and Tricks

This post discusses a few strategies that I have used to to manage memory in  R.

## Monday, November 16, 2009

### Site Map: Jeromy Anglim's Blog

This is an old version of the Site Map:

## Sunday, November 15, 2009

### How to Customise the Blogger Template

This post discusses how to modify the Blogger HTML template. For some time I have wanted to customise my Blogger template. I wanted to make various modifications including: adding a third column; increasing the overall width, customising the colour scheme; and more. This post documents my experience and lessons learnt.

## Monday, November 9, 2009

### Generalized Estimating Equations | General, R, and SPSS Resources

I was recently asked about Generalised Estimating Equations (GEEs). I haven't yet used the technique, but it's on my list of things to learn more about. This post catalogues some of the Internet resources on GEEs.

## Thursday, November 5, 2009

### Tips for Writing Up Research in Psychology

This post provides a list of links on writing in psychology with a particular emphasis on writing results sections.

## Monday, November 2, 2009

### Issues in Model Building and Parameter Estimation | Case Studies in Psychology

In this post I discuss issues related to Model Testing and Parameter Estimation. I focus on the role of this process in the scientific development of knowledge. I was motivated to write this post in an attempt to integrate the set of modelling issues that I was encountering across a range of psychological research topics including psychological tests, learning curves, social networks, and well-being. The post provides links to additional resources and presents some of my own observations on model testing and parameter estimation. I make the disclaimer that my ideas are still evolving on this topic.

## Friday, October 30, 2009

### How to Reason about Causes in Psychology | When does Correlation Co-occur with Causation?

This post is on causal inference. Errors in causal inference in the social and behavioural sciences are prevalent both in the scientific literature and in the media. This post (a) suggests articles on causality to read, particularly for researchers in psychology; (b) discusses and critiques material on the Internet on causality; and (c) provides further links to material on causality.

## Thursday, October 29, 2009

### Tips for Using StatET and Eclipse for Data Analysis in R

My favourite editor for conducting analysis in R is the StatET plug-in for Eclipse. This post discusses an assortment of tips and tricks that I've discovered to make this editing environment even better.

## Monday, October 26, 2009

### Scale Construction | Item Reversal, Scale Scores, Reliability, and Metadata

This post discusses how to: (a) use exploratory factor analysis output to determine items to retain on a test; (b) run syntax that reverses items and produces scale scores for a test; (c) calculate reliabilities for scales using retained items. Various tips are provided to make the process more efficient and less error-prone. The example uses SPSS, but many of the ideas would generalise to other statistics packages.

### Exploratory Factor Analysis and Scale Construction | R, SPSS, and General Resources

In this post I provide links to resources on exploratory factor analysis and scale construction. Links are provided for conducting exploratory factor analysis in R and in SPSS. Links to academic articles on the topic of exploratory factor analysis and scale construction with an emphasis on psychological applications are provided.

### Depth Interviews | Applications, Thoughts, Resources

This post discusses depth interviews. The post: (a) provides a range of applications where interviews may be useful; (b) makes a few observations from my experience; (c) lists additional resources for the interested reader.

## Saturday, October 24, 2009

### Data Mining and R

This post lists a few data mining resources in R. I also provide a few observations on the distinction between data mining, data analysis, and statistics as it pertains to the analysis work that I do in psychology.

## Friday, October 23, 2009

### Syntax Tips for Efficient Variable Selection in SPSS

This post discusses a few tricks for efficiently using syntax in SPSS. The suggestions aim to make variable selection more efficient and less error-prone. Specifically, an example is given of how to efficiently run a reliability analysis on a set of scales. The post is aimed at researchers using SPSS who are just starting to learn about the importance of Syntax.

## Wednesday, October 21, 2009

I have just started using Twitter. This post documents my experience. My aim is to give some suggestions to others who might be considering the adoption of Twitter.

## Tuesday, October 20, 2009

### Comments on "Data Intensive Scientific Discovery"

An interesting book has been published free online on the future of the scientific method and the role of computing, software, and information systems: Data Intensive Scientific Discovery
The ideas link in with the concerns of myself and others with reproducible research, data sharing, data analysis, and open publishing.

### What's in a Name? 21st Century Problems: Searching for PASW version 18

Most people now know that IBM has acquired SPSS, and SPSS the software product has changed it's name to PASW. I have often observed name changes with interest. Kentucky Fried Chicken (at least in Australia) decided long ago to change its name to KFC, possibly because Kentucky was too American, Fried implied  fat and unhealthy food, and chicken was too limiting. Likewise, SPSS decided long ago to distance itself from being just a statistics package for the social sciences.

IBM has now released version 18 of PASW. I was trying to find out what were the new features in version 18, when I stumbled on a potential problem with the new name, and perhaps some reasons why IBM may want to move out of troubling teen version numbers as quickly as possible.

### Focus Groups Should Not Be Used to Measure Attitudes of the Population | Myki Case Study

Victoria is in the process of adopting a new public transport ticketing system called Myki based on an electronic card. It's delivery is late and the project is over budget. The system has become a political issue. It was interesting to read the following statement:
"[MyKi project’s new spokeswoman] said that Government focus groups had shown that Melburnians were looking forward to using the new card." - TheAge
I just wanted to make a few comments about problems in the reasoning of the above quote.

## Monday, October 19, 2009

### Getting Started with Social Network Analysis

I have presented research on social network analysis to several forums including to organisational and educational psychology audiences. In these settings the audience varies substantially in their prior exposure to social networks analysis. Researchers new to social network analysis often then ask me where they should start in order to learn about the theories and methods of social network analysis. This post aims to provide some links to get such an interested researcher started.

### How to conduct a social network analysis: A tool for empowering teams and work groups

In 2007 I presented a talk discussing ways that social network analysis could be used as a consulting tool to improve team functioning. I'd earlier done some consulting work with Lea Waters applying social network analysis to understand team dynamics in professional white-collar teams. The experience highlighted the value of social network analysis as well as several of the methodological and practical issues that arise when using social network analysis as a consulting tool. The slides from the talk are made available to anyone interested.

### Job Satisfaction | Measurement, Scales, Facets

I was just reading through a section on job satisfaction in Landy and Conte's 2010 I/O psychology textbook Work in the 21st Century (3rd edition). The aim of this post is to comment on theories of job satisfaction and issues associated with job satisfaction measurement. I use Landy and Conte's text book (my favourite I/O textbook) as a frame of reference to guide discussion.

### Comments on the "R Clinic"

Theresa Scott runs an R Clinic at Vanderbilt. Researchers bring their questions along to weekly sessions and some answers are posted on this website.  It's great to see the combination of statistical consulting services and public posting of answers for the benefit of all.
Theresa has also developed a set of course notes on R, R Commander, Latex and Sweave, and Excel.

### Analysing ordinal variables

Ordinal variables create challenges for analysis. This post discusses: (a) definitions and distinctions related to ordinal variables, (b) theoretical issues related to ordinal variables, and (c) options for analysing ordinal variables.

## Friday, October 9, 2009

### Comments on "Ecological Statistics with R"

Didrik Vanhoenacker has put together a site called Ecological Statistics with R.

### Introduction to SPSS Syntax | Advice for Conducting Reproducible Research

This post provides an overview of SPSS syntax for researchers using SPSS. It sets out (1) why it is important to use syntax, (2) tips on how to use and learn syntax, (3) tips on dealing with errors; 4) tips on organising your syntax, (5) additional resources to learn more, and (6) where to go after you have reached the limits of SPSS syntax.

## Thursday, October 8, 2009

### Follow Up Tests in ANOVA in SPSS

This post discusses how to run follow up tests in ANOVA.

## Wednesday, October 7, 2009

### Factor Analysis in R

This post shows an example of running a basic factor analysis in R.

### Efficient Variable Selection in R

This post sets out my procedure for efficiently and reliably selecting variables from a data.frame in R

## Monday, October 5, 2009

### Blogs That I Follow

Besides Blogs on R, these are some blogs that I follow:

### Including R Code in a Blog Post

This post discusses ways of including formatted code in a blog post.

### Practical Tips on How to Conduct a Sophisticated Online Psychological Experiment

This post discusses strategies for conducting an online psychological experiment. The material was written in May 2008, and I have not yet got round to publishing it in an official outlet, and perhaps I never will. It's mainly just practical advice. Thus, it is provided online with the aim of sharing the ideas. I have other posts on Inquisit where I share sample scripts.

### My Software Setup

This post sets out the software that I am currently using.

### Analysis of a Multiple Choice Test | Getting Started

This post discusses how to perform a basic reliability analysis of a multiple choice test.

## Sunday, October 4, 2009

### Calculating Scale Scores for Psychological Tests

This post discusses how to calculate scale scores for multi-item scales. A lot of psychological research uses multi-item scales (e.g., personality tests, symptoms check lists, surveys, etc.). This post focuses on the issues involved with computing these scale scores.

### Producing a Table of Item Descriptive Statistics

The following post sets out how to present a table of descriptive statistics for a set of items using SPSS, Excel, and Word. At the bottom of the post, I've got an example of doing it in R.

## Saturday, October 3, 2009

### Creating Instructional Videos and getting Screen Captures with Jing

This post discusses one way of getting screen captures from your desktop and creating short instructional videos of actions on a computer.

### Scoring a Multiple Choice Test in SPSS using DO REPEAT

How do you score a multiple choice test in SPSS? This post shows you how.

### Data Mining and Statistics Video Course

David Mease has an online course presented with complete videos (Statistics 202: Statistical Aspects of Data Mining ). The course uses Excel and R.

## Friday, October 2, 2009

### Newspaper Reports IQ to be 180 | Is it True?

I was reading TheAge. Google is bringing out Google Wave. As part of the story they interview an Australian engineer on the project:
"Nigel, who has an IQ of 180, is also a maths whiz.." - The Age
This got me thinking. What does it mean to have a 180 IQ. IQ is a norm score. IQ typically has a mean of 100 and a standard deviation of 15. Thus, I asked the following questions:

• What's the probability of having an IQ of 180 or higher?
• One in how many people would have an IQ 180 or higher?
• What's is the probability that someone who a newspaper reports as having a 180 IQ or higher, actually has an IQ of 180 or higher?

### Windows XP Virtual Desktop Manager

This post discusses how to set up multiple virtual desktops on Windows XP. Some of the benefits are also discussed.

## Tuesday, September 29, 2009

### How to Write a Literature Review in Psychology

This post presents a set of principles on what makes a good literature review. The principles aim to assist students who are writing a literature review. Researchers preparing an academic publication may also find them a useful refresher. The principles pertain to dedicated literature reviews and introduction sections of empirical reports.

### Blogs on R | Statistics

What are the current blogs on R? What do they cover?

### Adjusting Correlations for Reliability | Attenuation Formula

This post discusses ways of adjusting correlations for reliability.

### Difference Scores | Are They Okay to Use?

A difference score is a variable that has been formed by subtracting one variable from another.
i.e., DIFFSCORE = VAR1 - VAR2.
Some researchers have heard that difference scores are 'bad'. This post discusses some of the issues, provides some additional references, and discusses calculating reliability of difference scores.

## Monday, September 28, 2009

### Psychology Statistics 101 | R or SPSS

Dan Wright has placed his Quantitative Methods 1 course online. The course offers instructions both in R and SPSS (PASW).

It is an interesting case study in  how to integrate R into a psychology quantitative methods course at the undergraduate level. It's also a cool example of integrating web resources.

## Saturday, September 26, 2009

### Classifying the Status of a Document with Quality Codes

I find it useful when preparing a journal article or thesis to think about the status of each section in terms of a rating from 0 to 10. I call this rating the quality code. To give the coding system substance each code has a label and a description. The codes and their groupings are listed below:

### Formatting a Table in Word | R to Tab-Delimited to APA Style

The following post sets out my procedure for importing a tab-delimited table of data produced in R  into Microsoft Word and formatting it.

### Grammar of Tables | Tables for Results Sections - Journal Articles and Theses

This post discusses ways of thinking about tables. What is the basic conceptual structure of a table? What are the implications of this conceptual structure for communicating with tables? How can this improve the quality of results presented in journal articles and theses?

### Item Parcelling in Confirmatory Factor Analysis

This post discusses item parcelling in the context of Confirmatory Factor Analysis. What is parcelling? How do you parcel? Should you parcel?

### Tetrachoric Correlations | Overview and Resources

What do you do if you want to run a factor analysis on a set of binary variables?

## Friday, September 25, 2009

### Discriminant Function Analysis in a Nutshell | Overview, Alternatives, and Resources

This post discusses Discriminant Function Analysis (DFA). It sets out the basic purpose of DFA and provides some links to additional resources.

### Spanking Lowers Child IQ | Correlation is not Causation

As I was waiting for a coffee this morning, I had a cursory glance at the paper and found The Herald Sun reporting on a study stating that:
"A SPANK on the bottom, long used by parents to discipline a naughty child, could cause more than tears... It's now thought the age-old disciplinary method may also lower a child's IQ, with those spanked up to three times a week having a lower IQ due to psychological stress."

## Thursday, September 24, 2009

### Recovering a Corrupted Excel 2007 File | XLSX and XLSM Format

An Excel 2007 file that I was working on recently became corrupted. The following are some things that I learnt in my process of recovering the file.

## Wednesday, September 23, 2009

### Statistics and Basic Data Analysis: Summary of Earlier Posts

I've recently activated Feedburner. It has not included my posts prior to March 2009. Thus, this post lists these earlier posts for any interested readers.
Statistics:
Writing:
And to put first things last:

## Tuesday, September 22, 2009

### Statistics Consulting: My Approach and Orientation

I've been a statistical consultant for postgraduate and fourth year psychology students for many years. The following post distils my method and philosophy of statistics consulting.

### "Why" and "How" to Subscribe to a Blog

This post sets out how to subscribe to my blog. It is designed for people new to RSS feeds. If all you want to do is find the RSS feed, here it is.

### Jeromy Anglim's Teaching Resources | Statistics

The following are some statistics teaching resources that I have developed over the years.

My list of academic publications has moved to here:

## Monday, September 21, 2009

### Linking text, results, and analyses: Increasing transparency and efficiency

I have recently been thinking about the relationship between text in a final report and data analysis. The broader concern is with making the conduct and reporting of statistical analyses more transparent. I am inspired by the ideas of literate programming, Sweave, and open access to data.

Something to aspire to:
• Raw data is shared  (ethics, copyright, and other considerations permitting).
• Code is shared that shows how the data was imported, transformed, and analysed. This code is well written, commented, and documented.
• The report is shared as opposed to requiring a paid subscription.
• Report output including tables, figures, and some text is linked directly to the analyses in code.

While the aspirations transcend R, I like the prospect of having analyses in R integrated with a final report. The inclusion of tables and figures , at least conceptually is a straightforward idea. However, the inclusion of text in a results section is a little fuzzier. Surely, text in a results section (I'll call it "results text" for short) varies in how it relates to actual analyses. Thus, I had the following questions: 1) What is the unit of results text? 2) How does results text vary and what should be automatically supplied by R?; 3) For results text that should not be supplied by R, how should it be integrated into an analysis process?

Initial thoughts: After a little reflection I had the following thoughts:

### Structural Equation Modelling in R

Structural Equation Modelling (SEM) Software is frequently used in psychology. This post discusses the exciting prospect of greater support for SEM in R.

## Saturday, September 19, 2009

### Introduction to Journal Article Deconstruction

One of the most powerful strategies that I use to learn how to write journal articles is to consciously study the writing conventions of good journal articles. I often want to communicate this strategy to other researchers who are battling the process of writing research. This is particularly the case with results sections. Thus, I plan to post various case studies using this approach to demonstrate how it works. Perhaps the principles generated from the deconstruction will also be relevant to others. I'll post all such instances with the label Article Deconstruction.

## Friday, September 18, 2009

### Variable Importance and Multiple Regression

Many researchers are interested in questions related to the relative importance of a set of predictors in multiple regression. This is important to both consultants and academics. I assume the motivation derives from the assumption (typically wrong at least to some extent) that the predictors flagged as important will have  larger causal effects and are therefore better targets for manipulation in an  intervention. Some examples include: a) a set of risk factors on clinical symptoms in psychology; b) a set of personality measures on performance; c) a set of beliefs on overall attitude.

### R Community in Australia

One of the nice aspects of R is the community of users that has built up around it. The open-source model seems to create an orientation of sharing and contribution. Users benefit from R and then they give back in the form of new packages, free documentation, blogs, presentations, and so on.

## Thursday, September 17, 2009

### Comments on "Introduction to Scientific Programming and Simulation Using R"

I've just been reading Introduction to Scientific Programming and Simulation Using R by Owen Jones, Robert Maillardet, and Andrew Robinson.

## Tuesday, September 15, 2009

### Setting up a Blog on Blogger

Given the number of academics in the world, there are surprisingly few blogs on psychology and research methods. There are many possible reasons. Two barriers are: 1) lack of knowledge of the ease of creating a blog; and 2) lack of knowledge of the benefits of having a blog.

The details below set out my setup for my blog account and my blogging statistics. When I set it up originally, I did look into the various options in terms of blogging providers and so on. I make no claim to my choices being optimal for me or other people. But I have found them more than adequate for my purposes. In particular, usage statistics (and comments) are a great form of feedback that is not necessarily available in other forms of academic communication. For further discussion of the benefits of blogging and related technologies in academic, Gideon Burton provides a great exposition.

### Confidence Intervals and Correlations

In a previous post, I discussed the various scenarios for running significance tests on correlations.

A researcher recently asked me how to calculate confidence intervals for two correlations that share a common variable (i.e., dependent correlations).

## Thursday, September 10, 2009

### Pen and Paper

For a long while I did almost all my thinking and writing either in my head or on the computer. More and more lately I find myself returning to pen and paper.
Examples:

## Wednesday, September 9, 2009

### Experiments with a mixture of repeated measures and between subjects factors

I often speak to researchers who need to analyse an experiment with a combination of between subjects and repeated measures factors.
Some Examples:
• 5 x 3 Design: 5 levels of task type (repeated measures); and 3 levels of group (between subjects)
• 2 x 2 x 2 Design: 2 levels of order (between subjects); by 2 levels of instructions (between subjects); by 2 levels of task feature (repeated measures)
This post directs such researchers to some resources on the web.

Resources:
• UCLA has several examples of how examine such designs using SPSS Repeated Measures ANOVA; It also talks about how to test contrasts and run follow up test more generally.
• Andy Field provides a gentle introduction to repeated measures ANOVA using SPSS.

## Tuesday, September 8, 2009

### Cluster analysis and single dominant factors

I often chat with researchers wanting to use cluster analysis to group cases. I just wanted to point out a common scenario where cluster analysis may not be a good way of proceeding.

## Monday, September 7, 2009

### Logistic Regression Resources in SPSS or R

Question: A researcher asked me: "What resources are available for running and interpreting a logistic regression?"

### Significance Tests on Correlations

OVERVIEW: I often speak to researchers wanting to compare the significance of two correlations. The two scenarios most commonly encountered are: 1) comparing dependent correlations; and 2) comparing independent correlations.

## Wednesday, September 2, 2009

### Repeated Measures Experiments with Many trials in SPSS (PASW)

I was recently talking to a researcher who was in the process of analysing experimental data based on a 2 x 2 x 2 x 4 repeated measures design. Each combination of the levels of the repeated measures factors involved five trials. The dependent variable was reaction time. The researcher had their data laid out in a one person per participant format (wide format). I had the following advice for the researcher:

Data Format:
Create a long format data file called “trials” where each row is the combination of one participant and one trial. And have a separate data file called “subjects” that contains one row per participant and includes data on participants that is constant throughout the experiment (e.g., gender, age, personality measures, etc.).

## Tuesday, August 18, 2009

### Social Network Analysis Resources for R

Social Network Analysis is an increasingly popular tool for modelling dependence structures between social actors. In my department researchers are developing new models for representing such dependence structures (MELNET). In 2007 I gave a talk on my consulting experience using social network analysis to provide insights on team dynamics. Since then I have switched to mainly using R for analysing social network datasets.

## Monday, August 17, 2009

### Selecting University Students: Perspectives from Selection and Recruitment

The discussion paper mentions other means for selecting students in addition to their performance in the final year of high school (ENTER).
I see the issue as involving two elements:

1. What criterion of an effective selection system does the university want to use?
2. What measurement system can be put in place to maximise this criterion?
The first issue is a matter of values and policy. The second issue is empirical.
From The Age article I gather that there is concern for: representation from disadvantaged student groups and academic potential.
Many other values could be mentioned, including transparency, procedural justice, cost of administration, and so on. No doubt any decision would be a synthesis of such concerns. However, if the choice of criterion could be resolved, the question of a measurement system is largely an empirical question.

## Wednesday, August 5, 2009

### My Procedure for Upgrading R: Windows XP with StatET

R releases upgrades around every 6 months. I run R on Windows XP using the StatET plug-in and Eclipse. This is my current upgrade procedure. I've posted this mainly for my own future reference. But who knows? it might be useful for someone else:

## Friday, June 12, 2009

### Redmond Barry Building Views: 4 Seasons in One Day

A series of pictures from my office window.

## Saturday, June 6, 2009

### Upcoming Conferences

I'll be attending a couple of conferences in Europe in early to mid July, 2009. So, if anyone who reads this blog will be attending, feel free to say hi.
1. 11th European Congress on Psychology in Oslo: I'll be presenting a talk: "The effect of warnings on personality test faking in employee selection"
2. Directions in Statistical Computing in Copenhagen

### Normality and Transformations: A few thoughts

A lot of researchers ask me about normality and transformations. This post sets out some my advice on assessing normality and dealing with violations of the assumption.

### Learning R for Researchers in Psychology

R is a powerful open source environment for statistical computing. This post provides a selective list of resources for getting started with R including thoughts on books, online manuals, blogs, videos, user interfaces, and more. At the end of the post are some R resources specific to researchers in psychology. (UPDATED 4th May 2011)

## Friday, May 29, 2009

### Pronunciation Guides for Mathematical Notation, Expressions, and Greek Letters

When doing research in psychology you are sometimes required to study new statistical or mathematical techniques on your own. However, mathematical books rarely tell you how to pronounce the mathematical symbols. And even if you know how to pronounce the symbols in isolation, this does not guaranty that you can pronounce a mathematical expression made up of multiple symbols. Being able to read mathematical notation is a basic first step in aiding memory and conceptual understanding. The following links provide resources on reading mathematical symbols and provide a good reference if you encounter symbols and expressions with which you are not familiar.

#### Mathematics Pronunciation Guides

• VÄliaho's guide to Pronunciation of Mathematical Expressions: This is the place to start. It covers many important rules in a 3 page document
• Handbook for Spoken Mathematics: If VÄliaho's guide did not meet your requirements, check out this extensive resource. It covers many major branches of mathematics such as logic and set theory, geometry, statistics, calculus, and linear algebra. It is the most comprehensive guide that I have found with around 100 pages and around 500 symbols with pronunciation. I'd recommend studying all the symbols if mathematical pronunciation is an issue for you. The symbols are distributed over many pages making it a little difficult to look up a single symbol of interest. Also, when a choice exists, the guide often chooses a more verbose and less ambiguous form of pronunciation. For example, it suggests for "x_i", "x sub i" instead of "x i". This emphasis on unambiguous verbal communication is sometimes more than required when verbalising the symbols in your head or when verbalising symbols in a context where the actual symbolic math is also displayed.
• RPI's Saying Mathematics Guide
• Oanca et al's Reading Mathematical Expressions
• Wikipedia guide to mathematical symbols: meaning of common mathematical symbols with links to their meaning.
• Greek letters: Lower and upper case Greek letters with pronunciation
• Tips on displaying formulas can even be useful for some obscure mathematical symbols
The other option is to actually listen to mathematics lecturers and assume that the pronunciation will rub off: see my earlier post on free online mathematics video courses.

#### Books on mathematical pronunciation

• Lawrence Change (1983). Handbook for Spoken Mathematics: (Larry's Speakeasy).

## Thursday, May 28, 2009

### Introduction to Statistical Modelling in Psychology: NSS Presentation

Today I gave an introductory talk for the Neuropsychological Students’ Society at the University of Melbourne on the topic of Statistical Modelling in Psychology.

The slides with notes from the talk are available for download at the following link: Introduction to Statistical Modelling in Psychology.

## Friday, May 22, 2009

### Bootstrapping and the boot package in R

I was recently asked about options for bootstrapping. The following post sets out some applications of bootstrapping and strategies for implementing it in R. I've found bootstrapping useful in several settings:

• where the statistic I'm interested in is a little unusual: the average R-square across five separate regressions; the difference in the average correlation of a set of variables between two groups
• non parametric statistics, such as the median
• when assumptions such as normality of homoscedasticity are not satisfied

## Thursday, May 21, 2009

### Self-Archiving of journal articles in academia

I'm a big fan of academics who post copies of their journal articles on their own website (e.g., here and here and here). Even if my university has online subscriptions to most journals, it is just more convenient to access all of a person's work in one place. Such articles are also typically then available through Google Scholar. It also opens the work up to others outside of academia who do not have access to university journal subscriptions. Given that academic work is typically directly or indirectly funded by public money, this seems particularly important.

I have found Sherpa Romeo to be a useful site for looking up the standard publisher copyright transfer agreement for different journals. This can be useful in selecting a journal outlet that allows for publishing on your own website. It also sets out the conditions for putting journal articles on your own website.

See here for a discussion of author rights.

## Wednesday, May 20, 2009

### Endnote Collaboration

I'm currently exploring options for using Endnote for collaboration:
UQ has a nice discussion of strategies for collaborating with Endnote.
I'm also considering using the Endnote web option.

## Friday, May 15, 2009

### Statistics for a Psychology Thesis

In 2007 I presented a talk to postgraduate psychology students at The University of Melbourne. As part of the talk I produced a handout which summarised many of the key points that I felt were relevant for such an audience who needed to complete a thesis involving quantitative analysis. Reading over it two years later, I still agree with the ideas, even if my understanding may be a little more nuanced. For example, I'd now see meta-analytic thinking as a simple version of Bayesian statistics. Anyway, I thought I'd post it on the blog.
The audio (17MB) for the talk is available online, as are the Slides, and a PDF version of the content below.

## Wednesday, May 13, 2009

### Online Mathematics Video Courses For Self Study in Psychology

This post provides links to free online video courses on mathematics and statistics.

### Verifying How Composite Scores Have Been Computed

This post sets out a procedure for checking how a composite was computed from items. This is particularly useful when working with self-report psychological scales and composite ability tests. Computing total scores for a series of subscales and total scores on personality tests and other self-report inventories can be fiddly business, and errors often arise.

## Wednesday, March 25, 2009

### Calculating Composite Scores of Ability and Other Tests in SPSS

Researchers in psychology often have a large number of variables. Science aims for parsimonious explanations of the world. Thus, the challenge is to develop a principled approach to dealing with the multiplicities that arise in psychological research. One common approach is to combine tests that measure similar things into composites. This post looks at how to form composites. The emphasis is on settings where you have multiple ability tests and you want to create a composite ability factor. Also, particular emphasis is given to how to do it in SPSS.

## Monday, March 23, 2009

### Inquisit: Simple Reaction Time, Four Choice Reaction Time, and Typing Test

In 2007 I was looking for a tool for running psychological experiments online. It was important that the online tool could record reaction time. After a little exploration I started using Inquisit.

I’ve attached a script that I wrote which provides a basic measure of simple reaction time, four-choice reaction time, and a typing test. I thought I’d make the script available for others to use and modify. The program was written for Inquisit 3.0. The Inquisit website has a pile of additional scripts. It also has a fully functional trial-version of the software.

Click on the link below to download the script. Change the file extension to ".exp" to associate with Inquisit.

## Saturday, March 14, 2009

### Photos from My Office - The University of Melbourne

For all its quirks, the Redmond Barry Building provides some very nice views.

### User Interface for R: StatET and Eclipse

R is tremendously flexible. It’s flexible in how commands can be written, and it’s flexible in the user interface that can be used to run it. I’ve been playing around with different user interfaces on Windows for a while now.

## Thursday, March 12, 2009

### Saving Citation Information from Google Scholar

I have often wanted to be able to export citations from Google Scholar into Endnote. While Google Scholar makes it easy to do this for single articles, it does not at present permit you to export an entire search.
I’ve found a work around. Anne-Wil Harzing’s Publish or Perish Software (free) searches Google Scholar and allows you to export a file that contains the ciation information of the entire search. This can then be imported into Endnote. It also exports in Bibtex and CSV format.
It’s also a great way to assess the impact and citation rates of individual scholars, journals, and particular articles.

## Friday, February 27, 2009

### Books on Writing, Grammar, and Style in Psychology and Beyond

This post lists some books on academic writing, which I've found useful.

## Thursday, February 19, 2009

### Assorted issues with Multiple Regression and Moderation

1. Do variables in moderation have to be normally distributed before centering?
No, normality is not a requirement. However, you could apply a transformation if you felt it was justified, such as when it better reflects the meaning of the variable.
See the following for a discussion of issues in transformations:

Assumptions in moderation are the same as in normal multiple regression. They mainly concern the pattern of the residuals. For a discussion see: http://www.statisticshell.com/multireg.pdf

2. Do I use the R squared or adjusted R squared when reporting a multiple regression?
You can use either or both. The larger your sample, the smaller the difference is between adjusted R square and R-squared. R-squared is a biased estimate.

3. p=0.52, is that still significant?
Jacob Cohen once said something along the lines that surely God must love .06 almost as much as .04.
You can write p = .05
Whether this is statistically significant depends on your alpha. If your alpha is .05, then your obtained p value is not less than .05, and thus, it is not statistically significant. Reflecting the seemingly arbitrary cut-off consequences off null hypothesis significance testing, researchers often write that there was a trend toward significance when p <.10 and >=.05.

4. Would a significance level of 0.06 be slightly significant or not at all?
Trend toward significance is a common label, see above.

5. Do you have any examples of how to write up a moderator regression?
Frazier, P., Tix, A., & Barron, K. (2004). Testing moderator and mediator effects in counseling psychology research. Journal of Counseling Psychology, 51, 115-134.

McAlister, A. R., Pachana, N., & Jackson, C. J. (2005). Predictors of young dating adults' inclination to engage in extradyadic sexual activities: A multi-perspective study. BRITISH JOURNAL OF PSYCHOLOGY, 96(3), 331.

### Single Group Correlational Study: Basic Analyses

This post sets a basic procedure for analysing a single group observational study in psychology. It aims to provide a starting point, particularly for researchers who do analyse data infrequently.

### Formatting Correlation Matrices in Psychology

Researchers in psychology often want to present a correlation matrix of the main variables in a study. This post sets out one way of producing a formatted correlation matrix that conforms to APA style.

## Friday, January 16, 2009

### Avoiding typing references into Endnote using Google Scholar

This post provides a tip for using Google Scholar to make importing references more efficient.

## Thursday, January 15, 2009

### Saving Tab Delimited Text Files in Excel without Warnings

Since using R, I have started generally storing my data in tab delimited text files. I tend to edit this data in Excel. Excel is easier to use than the current editor built into R.