Whenever something is being tested you need two groups (at a minimum) to get accurate results. These are often known as the experimental group and the control group. If you don’t have the testing set up in this fashion, it will be very hard to get usable results and almost impossible to have any kind of scientifically valid or accurate data.
Why are these groups called what they are, and what are the purposes of each?
Control group: This is the group of people (or animals, plants, or whatever is being used) that is used as a control. It is well known that you can not use the term you are defining in the definition but in this case, it pretty much fits. It is the group that nothing is done to change the outcome of the experiment. They are still under a certain amount of control but whatever is being tested is not used on this group. Basically this group will show you what happens if nothing is done at all, more or less if everything stayed the same as it was. It is the group that is in it’s natural (or as close as possible) state.
Experimental group: This is the other group. It could be said that this is the more important of the two groups. This is the one that is going to be watched. Whatever is being tested or changed will be done to this group. Any type of change, effect, or differences will be noted. It is better to have this group as large as possible (within reason) so you can better study the effects either good or bad.
It doesn’t matter if there is a study being done on a new wonder drug that can cure every known disease or testing which kind of tooth paste is more effective. You have to have both of the groups. The control group will give you recorded results on what happens with out the substance being tested. Many times a placebo, or imitation, product will be used so psychologically there isn’t any difference in the groups.
Once the experiment is finished, any differences between the control group and the experimental group will be studied. This will show the effectiveness, if any, of the substance that is being tested. This concept will work for looking for both positive and negative effects of a product.
Other than items that may be made for public consumption, anything that will come in contact with people will be required to be tested in a manner similar to this. Why would it have to be tested this way? Think back to the turn of the 20th century. All of the fake medicines that were sold through catalogs and traveling salesmen. These items were never tested to see if they had any kind of medical effect (and as it turns out, many were actually dangerous). Doing studies with 2 sets of groups, the experimental and the control, lets you see what the effects of any given product is.
Basically, you have something that you want to find out what it does. Put people into two groups. The first group doesn’t get anything but a fake version of the substance. This is called the control group. The second group is the one that receives the substance. This group is called the experimental group because you are conducting experiments with this group. The differences between the two groups will show what the effects of the test material may be.