This video, we're going to begin talking about experiments. An experiment is a controlled test where one variable is manipulated to discover its effect on another variable. The variable that is manipulated is our independent variable, which we theorize will have an effect on our dependent variable. The independent variable is manipulated, and the dependent variable is measured. In an experiment, we place our participants into groups, and we do that through a process called random assignment.
In random assignment, we place our participants into their condition or group at random. The idea behind this is that we're trying to increase the equivalency between groups. We want our groups to be as equal as possible on any potential confounding variables because we want our groups to be the same so that the only difference between them is the manipulation of the independent variable. When we get our result, we can very confidently say, "The only difference between these two groups was the independent variable, so that must be what caused our result to happen." If there is no equivalency between the groups, we can't make that conclusion as definitively. For example, if the average age of your first group is 50 and the average age of your second group is 20, when you get your result, you could say, "Maybe it was an age effect. Maybe they interpreted the instructions differently." If one group is mostly male and one group is mostly female, you could say, "Maybe it was the independent variable, but maybe it was a gender effect that we found." This can be true of any variable.
You don't want one group to be more motivated or more tired, or have a higher IQ on average. By randomly placing our participants into groups, we're going to be increasing the equivalency, ensuring equal numbers of males and females, even distribution of age, etc. When our groups are equivalent, we can be more confident that what we are finding is the effect of our independent variable on our dependent variable. With an experiment, you are going to have an experimental group or potentially multiple experimental groups. This is going to be the group or condition in which the independent variable is manipulated or is present.
The experimental group is where we are actually going to be observing the effect of the independent variable on the dependent variable. We're also going to want to have a control group, which is a group or condition in which the independent variable is absent. The idea here is that we want to be measuring our dependent variable as it would occur naturally without the independent variable. At the end of our study, we can compare these groups, and if they are different, we can assume that the independent variable must have had an effect on the dependent variable. To give you an example, let's just say we have a hypothesis that listening to classical music while studying is going to increase test performance.
The classical music, or the auditory environment of your studying, is our independent variable because we believe it's going to have an effect on test performance, which is our dependent variable. For our method, we're going to have students come into our lab. They will study a brand new topic that they've never learned before for 1 hour, then they're going to take a test, and we will be assessing, of course, their test performance. So we are going to have 3 experimental groups to make this a very scientifically rigorous study. In group 1, we're going to be directly testing our independent variable and will have that group listening to classical music.
Okay, but then someone might say, "Is it classical music, or is it any kind of music?" That's a great point. Let's address that with group 2, which will listen to pop music. Now we're kind of getting at, "Is there something really special about classical music as I'm hypothesizing, or is it just music in general?" But then someone could say, "Maybe it's not music. Maybe it's just noise." That's a good point. Let's have group 3 listen to ambient cafe noises. There's no music present, but we have a sound environment at an equal decibel level to our musical conditions. Then we'll have our control group, of course.
Group 4 here is going to have some noise-cancelling headphones, and they will hear no sound. So there is absolutely no auditory environment happening for group 4. We're just going to see test performance under naturally occurring conditions. Ultimately, we will randomly assign people into these groups, and then we're basically just statistically comparing the test performance of these groups. What we're hoping to see is that group 1 has a statistically significant higher test score than the other three groups, which would give us evidence for our hypothesis being correct. Alright. So that is our little example of an experiment. We're going to keep talking about experimental design in our next video, so I will see you guys there. Bye bye.