Question

question
a 2013 study at johns 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 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?
select the correct answer below:
○ short term memory
○ whether or not a person received caffeine
○ how many images could be remembered
○ the number of people in the study

Explanation:

An explanatory variable is the one that is manipulated to see its effect on the response variable. In this experiment, the researchers manipulated whether a person received caffeine (giving half caffeine and half placebo) to see its effect on short - term memory. "Short term memory" and "How many images could be remembered" are response variables (what is being measured as an outcome). "The number of people in the study" is just the sample size and not a variable being manipulated to see an effect.

Answer:

B. Whether or not a person received caffeine