A random sample of 60 mathematics majors spent an average of $200.00 for textbooks for a term, while a random sample of 40 literature majors spent an average of $180.00 for textbooks that term. The standard deviation for each sample was $20.00. The standard error for the difference between the two sample means is 4.082. Calculate an approximate 95% confidence interval for the difference in average amounts spent on textbooks (math majors - literature majors).
A) (7.8, 32.2)
B) (11.8, 28.2)
C) (15.9, 24.1)
D) None of the above

Question

Quizplus · Accepted Answer

The difference in sample means is $200 - $180 = $20. The 95% confidence interval is calculated as the difference in means ± 1.96 * standard error. Thus, $20 ± 1.96 * 4.082 gives the interval (11.8, 28.2).

A Random Sample of 60 Mathematics Majors Spent an Average