The participants themselves can actually affect the results of an experiment. We know that we can’t study everyone in the world in a psychology experiment. We may only have 100 people to study, so we want to make sure that we are fair in how the experiment is carried out with those 100 people.
For example, we want to find out if distraction affects recall of 50 words. We split participants into two groups. We put all the men in group 1 and all the women in group 2.
Group 1 – Have to listen to loud music while trying to learn the words.
Group 2 – Sit in a quiet room to learn the words.
We ask all participants to read a list of fifty words. Then at the end, they have to remember as many as they can. We might find a difference in the results, but it could be due to gender differences in memory rather than distraction.
|Variable||Way to Control For It|
|Participant effects||Random Allocation – One way to control for issues like this is to randomly allocate people to conditions. So we might have our 100 participants and randomly split them into two groups. For example, putting all the names into a hat then picking out one for group 1, one for group 2, one for group 1 and so on. This ensures that the groups are more randomly selected.|