You are evaluating investing in a cognitive training company.For this reason, you want to determine whether users who complete at least 75% of the recommended daily training for two months show improved levels of reading comprehension and problem-solving skills.You select a random sample of new users and get test scores for each participant in the sample.The test score is a composite of reading comprehension and problem-solving skills.Two months later, you randomly select 15 users from the original sample who have completed 75% or more of the recommended training in the last two months and have them take a test similar to the initial test.You are interested in determining whether the average test score before training is different than the average test score after training for this sample.The after-training average is 92.8, which is 2.7 points higher than the before-training average.The sample standard deviation of the differences is 1.2.You can assume that the differences are normally distributed in the population.The degrees of freedom for this test are ______.
A)30
B)29
C)28
D)15
E)14

Question

Quizplus · Accepted Answer

The degrees of freedom for a paired samples t-test (which is appropriate in this scenario since the same participants are measured before and after training) is calculated as the number of pairs minus one. Since there are 15 users (or pairs) in the sample, the degrees of freedom are 15 - 1 = 14.

You Are Evaluating Investing in a Cognitive Training Company