Incoming freshmen are given entrance examination in a number of fields including English. Over a ...

incoming freshmen are given entrance examination in a number of fields including English. Over a period of years, it has been found that the average score in English examination is 80 with standard deviation of 7.8. An English instructor examines the scores from his class of 40 and finds their average in 85. Can the instructor claim the average scores has increased at 0.05 level of significance?

Critical value?

Computed Value?

conclusion?