by Paul Rose, Psychology Department, Union College
I have always been surprised by how many psychology students confuse random assignment and random selection on assignments and exams. My best guess is that this confusion stems from their paying too much attention to the word "random" and not enough attention to the words "assignment" and "selection". Accordingly, I have developed two very simple visual demonstrations that may help students see the difference. They aren't fancy, but I think they do the job.
Feel free to adapt these demonstrations however you wish for your own purposes. I have made each demo freely downloadable precisely so that any educator can use them for any benign purpose they wish.
Keywords: random sampling assignment psychology research methods experimental experiment survey questionnaire investigation observation statistics inferential