Suppose that simple random samples of college freshman are s

Suppose that simple random samples of college freshman are selected from two universities - 15 students from school A and 20 students from school B. On a standardized test, the sample from school A has an average score of 1000 with a standard deviation of 100. The sample from school B has an average score of 950 with a standard deviation of 90. What is the 90% confidence interval for the difference in test scores at the two schools, assuming that test scores came from normal distributions in both schools? Please Explain where your numbers are coming from.

Solution

n1 = 15

n2 =20

Confidence interval:
  The mean of Group One minus Group Two equals 50.00
  90% confidence interval of this difference: From-181.0.02, 231.0302