11 5 points Exercise 1515 How tall are children these days

11. ( 5 points) Exercise 15.15 How tall are children these days? Example 14.1 (page 336) assumed that the heights of all American eight-year-old boys are normally distributed with standard deviation =10 cm. How large a sample would be needed to estimate the mean height in this population to with 1 cm with 95% confidence?

Solution

Compute Sample Size
n = (Z a/2 * S.D / ME ) ^2
Z/2 at 0.05% LOS is = 1.96 ( From Standard Normal Table )
Standard Deviation ( S.D) = 10
ME =1
n = ( 1.96*10/1) ^2
= (19.6/1 ) ^2
= 384.16 ~ 385