To investigate the efficacy of a diet, a random sample of 16 male patients is drawn from a population of adult males using the diet. The weight of each individual in the sample is taken at the start of the diet and at a medical follow up 4 weeks later. Assuming that the population of differences in weight before versus after the diet follow a normal distribution, the t test for related samples can be used to determine if there was a significant decrease in mean weight during this period. Suppose the mean decrease in weight over all 16 subjects in the study is 3.0 pounds with a standard deviation of differences computed as 6.0 pounds.
Referring to the table above, the t test should be _______ - tailed
Answer: One tailed test
This is a before and after test. We are testing whether the weight after taking the diet has decreased.
Though this has not been asked in the problem, we can test the hypothesis
M = Mean of difference= 3 pounds
The solution performs a t test for testing hypothesis.