Question

A 2013 study at John's Hopkins University wanted to measure if caffeine has an effect on short term memory. The researchers showed images to a group of people. They then gave half of the group a 200 mg caffeine pill and the other half a placebo pill containing no caffeine. A day later they measured how many images each person could remember. What is the explanatory variable in this experiment?

Answer 1

We will have that in this case the explanatory variable will be the placebo pill. Since it will be used to study the effect of not really using caffeine in the data.