summarize in an experiment, participants are randomly allocated to different conditions which form the different levels of the independent variable. In a correlational study, participants are not randomly allocated to different conditions; data on the independent and dependent variables is collected for the respondents and the relationships between them are investigated. There are two types of data: frequency and numerical. Frequency data involves counting how many people fall into a particular category. Numerical data involves measuring how well people performed by assigning a numerical value to their performance. ANOVAs examine the differences between group means when there are more than two groups, are able to consider the effect of more than one independent variable and can reveal whether the effect of one of them is influenced by the other. Basic Features of Statistical Analysis and the GLM 13 01-Foster-3327(ch-01).qxd 10/13/2005 10:21 AM Page 13 The general linear model (GLM) is a statistical theory which underpins many parametric analytic techniques. The general aim of methods underpinned by the GLM is to determine whether the independent variable(s) affect or relate to the dependent variable(s)