Carlos, the president of a fraternity on campus, randomly sampled 500 students, asked them if they belonged to a fraternity or sorority, and asked them about their current GPA. He discovered that the GPAs of those people in fraternities and sororities were higher than those of people who were not involved in the Greek system. Gleefully, he presented his findings to the dean, saying that being involved in a fraternity or sorority leads to higher grades. What rule of research methods is Carlos breaking? A. Correlation does not equal causation.
B. College students are not representative of the whole sample of people in the world.
C. His sample size of 500 is too small to make such a generalization.
D. Correlational data do not provide any practical information on a topic.

Correlation is simply the measure of how closely related two things are. In statistics a number is usually used between -1 and 1 with 1 being perfectly positively correlated and -1 being the opposite.

It is important to note that just because things correlate does not mean that one causes the other. There is sometimes a third factor that influences things.

A commonly cited example is that people spend more time in stores during winter. This could mean that the cold keeps them in the shops to remain warm but the more logical reason would be that winter coincides with the festive seasons so people may be buying gifts .

So just because people in Sororities and Fraternities are performing better does not mean that being in the Greek system is the reason for this.