Hello everyone, and welcome to the seventh chapter of the University of Southern Queensland’s online, open access textbook.
The aim of this seventh chapter is to discuss the use of two specific types of covariates: moderator and mediator variables. Moderator and mediator variables function in respect to a relationship between two other variables, such as reading ability and test performance. In a sense, moderator and mediator variables are simply special types of covariates. However, in the case of a moderator variable, the moderator functions by changing the strength or magnitude of an existing effect between two variables. For example, in the case of reading ability and test performance a third variable, such as anxiety, may change the pre-existing relationship between reading ability and test performance. In the case of a mediator variable, there is some amount of the effect between the two existing variables that is transmitted through the mediator. For example, in the case of reading ability and test performance, perhaps reading ability must function at least in part through a third variable such as attention capacity to effect test performance.
There are some slides that appear via links within Chapter Seven. Please look for these as you review the current chapter.