Statistical tests are run to determine if the results obtained with a sample of the population can be applied to the entire population. We make an inference about the population. In order to make an inference, we run a statistical test

Studies typically are done with a sample of the entire population.

We try a weight loss program with 50 college females, not all college females in the world. But we want the results of our study to be applied to all adults. How can we do this?

We can run a statistical test to make a decision, estimation, prediction, or generalization about the population based on information from our sample. This is called a statistical inference.