Professor Smith took a sample of 191 students from her morni

Professor Smith took a sample of 191 students from her morning class and a sample of 120 students from her evening class. On Exam 1, all those sampled from the morning class got a 67 while those sampled from the evening class averaged a 69 with a variance of 166. If Professor Smith combines these two samples

Solution

combined variance = p(1-p)/n

Combined std deviation = 0.02812