Question

There is a positive correlation between high income and a high college grade point average. Are there any confounds or extraneous variables in the study?

Answer 1

Answer:

A correlation is only a mathematical means of describing the relationship between variables.  When it is a positive correlation, it means when the value of one increases, for example, the value of the other variable also increases or when one decreases, so does the other.  A negative correlation would show that as one variable increases in value, the other decreases.  These relationships are non-causal as you're not manipulating variables to control them to see what is causing this relationship.  Sometimes, non-causal covariance (or variables that don't have an effect on each other vary cooincidentally in a pattern-like fashion, when there is actually another variable causing the relationship going on.

Explanation:

In the case of this example, it is doubtful that having money causes you to have a higher grade point average.  So while we see an increase in grade point average with those who have high income it could be due to other factors, like people with more money have access to learning tools, tutors and other things that people with less money don't have access to.  So it is access to tools, not money that is actually causing a difference.  There are likely dozens if not hundreds of other potential confounded variables that could be causing this observation.