3.6 Summary

In a research study, we are usually exploring relationships between a response variable and explanatory variable. However the values of the response variable can be influenced by things other than the explanatory variable, such as other variables that aren't really of interest (extraneous variable), the study design and by chance. Some extraneous variables are also related to the explanatory variable, and are called confounding variables (and are lurking variables if they cannot be measured, assessed, described or recorded).