Question

You have been asked to build a confidence interval of the population mean starting salary for registered nurses in the United Stats. You already know that the population standard deviation for starting salaries is $7000 per year, and you want a margin of error no greater than plus or minus $1000. What is the minimum sample size that you should gather. If you want to have a level confidence of 95$%?

Answer 1

Solution :

Given that,

Population standard deviation = = 7000

Margin of error = E = 1000

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.96

sample size = n = (Z/2* / E) 2

n = (1.96 * 7000/ 1000)2

n = 188.24

n = 189

Sample size = 189