It is also possible that the order in which people take the tests influences the result (e.g. by conducting the test with beer a day after the test with wine. This can be corrected by sufficiently separating the tests, e.g. The problem with this approach is that it is possible that the results of the second memory test will be lower simply because the person has imbibed more alcohol. Also since the sampled subjects are the same for beer and wine there is less chance that some external factor ( confounding variable) will influence the result. The advantage of this second approach is the sample can be smaller. This is the approach used with paired samples.
This is the approach with independent samples.Īnother approach is to take a sample of 20 people and have each person drink a glass of wine and take a memory test, and then have the same people drink a glass of beer and again take a memory test finally, we compare the results. Paired samples are also called matched samples or repeated measures.įor example, if you want to determine whether drinking a glass of wine or drinking a glass of beer has the same or different impact on memory, one approach is to take a sample of say 40 people, and have half of them drink a glass of wine and the other half drink a glass of beer, and then give each of the 40 people a memory test and compare results. Unlike the hypothesis testing studied so far, the two samples are not independent of one another. Each set of measurements is considered a sample. In paired sample hypothesis testing, a sample from the population is chosen and two measurements for each element in the sample are taken.