A health worker is interested in determining if omega-3 fish oil can help reduce cholesterol in adults. She obtains permission to examine the health records of 200 people in a large medical clinic and classifies them according to whether or not they take omega-3 fish oil. She also obtains their latest cholesterol readings and finds that the mean cholesterol reading for those who are taking omega-3 fish oil is 18 points lower than the mean for the group not taking omega-3 fish oil. This is an example of

A t-test is a statistic test from which inferences can be drawn based on weather the difference in the means of two sample groups that could have particular common characteristics. The t-test is used for data sets that are normally distributed and the variance may be unknown

The t-test is used to test a proposed hypothesis (assumption) about a population

Therefore, based on the interest of the health worker to determine if omega-3 fish oil can help reduce cholesterol in adults by finding the difference in the means for the group taking omega-3 fish oil and the group not taking omega-3 fish oil, from which it can be determined if the difference in mean is statistically significant, is an example of a t-test