What is the purpose of a control group conducting a research study?

So you can see if the thing your testing really had an effect. For instance, if you just took ten mice and gave them ecstasy, yes, they might do soe,thing interesting, kr they might not, but whatever happens, you have no way of knowing if that is different from a normal mouses behavior. You need a group that is under conditons that are as close as possible to the treatment group(s), except for the variable you are tesing, so the. You know any difference between the groups is a result of the variable. Of course, to be sure you should use statistical analysis to see if the differences are statistically significant. For instance, if you were testing types of ferilizer, and half of the plants in your test group rew a foot tall, while the rest grew around six incues, even if all the plants in the control group grew shorter than all the plants in your treatment group(s), you couldnt comclude that fertilizer had an effect on plant height, since there was such a discrepancy between the olants in your comtrol group. What it come down to is this: you want the differences between groups to be greater than the differences between samples with in your groups.