A random sample of size 30 is taken from a normal distribution with standard deviation 9. The sample mean is 90. a) Find a 90% confidence interval for the mean ? of the distribution. b) Find a 95% confidence interval for the mean ? of the distribution.

A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
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Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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A random sample of size 30 is taken from a normal distribution with standard deviation 9.

The sample mean is 90.
a) Find a 90% confidence interval for the mean ? of the distribution.
b) Find a 95% confidence interval for the mean ? of the distribution.

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