SOLUTION: Based on a sample of 200 textbooks at the store, you find an average of 88.75 and a standard deviation of 12.8. The 95 % confidence interval (use z*) is: _____ to ____ (to 3

Algebra ->  Probability-and-statistics -> SOLUTION: Based on a sample of 200 textbooks at the store, you find an average of 88.75 and a standard deviation of 12.8. The 95 % confidence interval (use z*) is: _____ to ____ (to 3      Log On


   



Question 1119962: Based on a sample of 200 textbooks at the store, you find an average of 88.75 and a standard deviation of 12.8.

The 95 % confidence interval (use z*) is:
_____ to ____ (to 3 decimals)

Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
the half interval is z(0.975)*sigma/sqrt(n)
This is 1.96 *12.8/sqrt(200)
=1.774
the CI is 1.774 on either side of the mean
(86.976, 90.524)