Title: Introducing a control variable to a cross-tabulation
Course: UGQuants (SSPS) > Section: Causality

Introducing a control variable to a cross-tabulation

The following examples show you the respective analyses of the relationships between two categorical variables. In this sort of situation, with secondary data, we cannot control by manipulation. Instead, we have to control using statistical methods. We do this by identifying variables we may wish to control for and examine the relationship between our variables of interest separately for different values of our control variable.

If we find that the correlation is still as strong when we hold our control variable constant in this way, we can provisionally conclude that some causal process may be at work. If, on the contrary, the correlation changes, we face a range of different possible situations which we will explore subsequently.

Let us look at an example to demonstrate the impact that controlling for a third variable can have when looking at a possible association between two indicators: