In school, the only experiments we knew were those in the science lab, where you are asked to put on your white coat and watch the teacher mix sodium hydroxide with hydrochloric acid, that a few years later you were taught to mix them yourself , producing sodium chloride and water. The normal acid + base reaction, that always produced salt and water.
Growing up, maybe by the time you finish your bachelor’s to the time you study for your master, you are required to prepare your own thesis to graduate. When going through the rules each thesis should contain and how to properly write down your thesis, you will find out the elements you need to qualify your thesis.
Especially if you are a science student, your thesis will contain experiments that would need to be objective.
To objectify your experiments, you will need to make some tests of significance to whatever you are experimenting. These tests include T-tests and the Chi test.
The significance level is known in a manner such that if the calculated P-value is less than or equal to the critical value, this dictates a highly statistically significant difference that can not be ignored. If the P-value is more than the critical value, it means that the difference between the groups is insignificant. It could be due to human error, and it may be ignored.
So what exactly are we comparing?
Let’s say that you are trying out the effect of a new drug, that is supposed to cure a specific disease, depression for example. You will need to have two or more groups of people. For the fairest experiment, all groups should be treated in the same way, living in the same atmosphere and dealing with the same things every day.
You may choose to name your groups (Group 1, Group 2, etc..).
If you have two groups, one group will be your experiment group, while the other one will be named your control group.
The experimental group is the group of, several numbers of, people suffering from the same stages of depression that you will actually try your drug on.
The control group is the group that you will be comparing your other experimental groups with.
In the case above, where you are testing the success of a drug on depression in people occupying the same place, time, food and treatment, the level of depression, being the independent variable, is the main focus of the experiment. The level or stage of depression is measured in several ways, one of them is using the Beck Depression Inventory (BDI). It is spread and well-known. BDI helps to measure the behavioural manifestation and severity of depression. This happens when the patients answer a questionnaire or, twenty one self-reporting questions, in a multiple choice response format.
Group 1, the first experimental group could get the right dosage that is tested to produce an effect against depression or maybe cure depression.
Group 2, the second experimental group could get half the dosage given to the first group, or it could be given another dosage that could be tested to create a successful drug that is against depression.
The third group would be the control group of the experiment. The patients will not be receiving any dosage of the drug being tested. Instead, they will be asked to intake a placebo. A placebo is a medicine or a procedure that is prescribed for a patient; for a psychological benefit, rather than a therapeutic or a physiological benefit. It could be an empty capsule or a vitamin tablet, that looks identical to the tablet administered to the first two groups.
This enables the one performing the experiment to value, measure and compare the groups – the dosage and the significant effect of the drug – on the patients. So if the patients in groups one and two do not show any difference to the placebo control group, it would lead to the understanding that the drug could still be processed and other elements could be added to produce a successful drug. This helps in drug testing as well.
The number of groups you can contain in your research is dependable on what you are studying. You can also consider giving one of the groups (not the control group) medicine that is already approved to cure or decrease depression levels.
The usage of control groups is not only used in experimental research, although that is what they are mostly used in, but, they can also be used in other researches like quasi-experimental and matching design researches.