Question 266356
A sociologist develops a test to measure attitudes about public transportation, and 27 randomly selected subjects are given the test. Their mean score is 76.2 and their standard deviation is 21.4. Construct the 90% confidence interval for the mean score of all such subjects. You may assume the scores are normally distributed. 
-------------
sample mean = xbar = 76.2
standard error = E = zs/sqrt(n)
E = [invT(0.95,df=26)*21.4/sqrt(27) = 1.7056*21.4/sqrt(27) = 7.0245..
--------
90% CI: 76.2-7.0245 < u < 76.2+7.0245
============================================
Cheers,
Stan H.