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A test about AIDs was given to 21 MIT students and 25 MCPHS students. The results as follows:

MIT: x=72.5 , s=12.6

MCPHS: x=76.5, s=10.8

a. Based on these data, can we say in general MCPHS students have higher score than MIT

students? Use=2.5%.

b. Find 99% confidence interval for the difference between MIT and MCPHS students' scores.