Welcome

Welcome to this course on statistical testing. The course has been written for students studying the AQA A Level Psychology specification, but it is also likely to be suitable for other specifications too (check your spec). Please watch the video below for an overview of the scope of the course.

After you have watched the video, scroll down to read the objectives and find out what is meant by the term inferential statistics and how they differ from descriptive statistics.

Clicking on complete and continue at the top will move you onto the next lecture, but make sure you have scrolled all the way down the page so you don't miss anything.

Objectives

In this course you will learn about:

• the difference between inferential statistics and descriptive statistics
• what is meant by testing for significance
• what is meant by a level of measurement and be able to identify examples of nominal, ordinal and interval data
• what is meant by related and unrelated samples
• the difference between tests of difference and tests for correlation
• when to use each of the statistical tests
• the difference between a parametric and non-parametric test
• how to apply and interpret significance levels
• finding and using critical values in statistical tables
• interpreting the outcome of a statistical test
• type I and a type II errors and now how to reduce the risk of making these
• reporting the outcome of a test
• how inferential statistics appear in the write up of a scientific report

Inferential Statistics

Statistical tests are part of inferential statistics. Hopefully you are already aware that there is a difference between descriptive statistics and inferential statistics, but just in case you are not I will outline the difference here.

Descriptive statistics provide a summary of the data that has been gathered. As the name suggests, they describe the data. For example, you might summarise and organise your data by calculating the mean and range of scores from 2 groups of participants so that you can make comparisons. Descriptive statistics also include the use of tables, graphs and charts to represent the data. Descriptive statistics are not covered in this course, but you can find a course dedicated to them on this site.

Inferential statistics, in contrast, are used to draw conclusions (or inferences) from the data. In Psychology we use statistical tests to work out whether the data shows a genuine effect in order to draw a conclusion, that goes beyond the immediate data, about human behaviour.