Question: State College is evaluating a new English composition course for freshman. A random sample of n=25 freshman is obtained and the students are placed in the course during their first semester. One year later, a writing sample is obtained for each student and the writing samples are graded using a standardized evaluation technique. The average score for the samples is M=76. For the general population of college students, writing scores form a normal distribution with a mean of µ=70.

a. If the writing scores for the population have a standard deviation of ð=20, does the sample provide enough evidence to conclude that the new composition course has a significant effect?

b. If the population standard deviation is ð=10, is the sample sufficient to demonstrate a significant effect? Again, assume a two-tailed test with ð=.05.

c. Briefly explain why you reached different conclusion for part (a) and part (b).