Soy bean type 1 yielded 125 bushels per acre last year at a research farm. This year, soy bean type 2, planted in the same location, yielded only 100 bushels per acre and there was a drought. The researchers do not know whether the difference is a result of the superiority of type 1 soy beans or the drought. What is this an example of?

confounding variables

Step-by-step explanation:

Confounding variables are outside influence that changes the effect of a dependent and independent variable. In this case the outside variable is the drought, which has changed the effects of the dependent and independent variables. This additional influence can be used to influence the outcome of an experimental result. Confounding variables can ruin an experiment and produce unwanted results.