1. A covariate is a variable whose effect a researcher has decided
to eliminate to see what the world would look like without it.
FOR EXAMPLE:
A researcher is determined to see if there is a relationship between driving speed and
a driver height with the hypothesis that the taller you are the faster you drive.
However, she is worried that gender might actually be a more influential variable
than height and decides to eliminate it’s effect. In this way she will be able to isolate
the unique effect of driver height on speed minus the influence of gender.
You can tell you have a covariate in your problem if you see expressions like this:
“Control for”, “eliminate the effect of”, “partial out”, or “hold constant”.
GENDER is the covariate because we are seeing what happens to
the relationship between driver speed and height if we eliminate
the effect gender.