As a chartered clinical psychologist within the British Psychology Society, I get sent a magazine called “The Psychologist” every month. In the August 2013 issue there was an article called “Why are effect sizes still neglected?” by Peter Morris and Catherine Fritz. The gist of the article is that when psychologist evaluate treatments using hypothesis testing, the results are often misleading. In particular, if you have large enough sample size you will almost always get a statistically significant result, even for minor and inconsequential effects. Consequently, it is important to always report an effect size when publishing results in an academic journal.

A common way to establish the effect size is to compare the symptoms for patients before and after a treatment. In the following video I give a tutorial on how to use data stored in an Excel spreadsheet with the AI-Therapy effect size calculator (it’s best to view full screen at 720p HD):


Fjola  Helgadottir, PhD, MClinPsych, is a clinical psychologist, a senior research clinician at the University of Oxford, and is a co-creator of, an online CBT treatment program for overcoming social anxiety


You may have noticed we have been a little slow on the blog updates lately. The reason is that we have been very busy working on our new product, and are pleased to announce:


Statistics for Psychologists

This is a little different than our core area (online self-help), so let me explain why we’ve created it. There are lots of statistics programs out there. However, some of them are hard for non-statisticians to use, some are expensive, and most require you to install software on your computer. We wanted something accessible, easy to use, and not loaded with options we don’t need. Given our extensive background in statistics and software, we decided to create our own solution.

These are our target audiences:

  1. Academia: The online calculators provide academic researchers with tools to help them distinguish between effective and non-effective therapies. Naturally our focus is psychology, but the tools themselves will be equally useful to researchers in any field.
  2. Clinicians:  Too often clinicians never give stats a second thought after they finish their degree. However, chances are that you are surrounded by interesting data in your clinic. We encourage you to run some therapy data through the program, as you may be surprised by what you find!
  3. Students: Learning stats isn’t easy. What we’ve created is something between an online tutorial and an interactive calculator. One way to learn the concepts is by interacting with the tools and visualizations. Try to get a feel for how changes to the input impact the results.
  4. Everyone else: Statistics is much more important in our day to day lives than most people give it credit for. In particular, it helps us make sense of the world around us. Take the plunge, and see what it’s all about!

Please get in touch and let us know if you have any feedback or feature requests. Also, help us spread the word if you know of anyone who might find this useful.


Sample graph from AI-Therapy's Statistics for Psychologists