Question

The monthly starting salaries of students who receive an MBA degree have a population standard deviation of $120. What sample size should be selected to obtain a .95 probability of estimating the population mean monthly income within a margin of $20? [sample size]

Answer 1

138

Explanation:

Population standard deviation =
`\sigma = 120`

.95 probability of estimating the population mean monthly income within a margin of $20

So, Significance level = 1-0.95 = 0.05

α =0.05

Margin error = 20

`ME =Z * (\sigma)/(√(n))`

Z at 0.05 = 1.96

`20 =1.96 * (120)/(√(n))`

`√(n) =1.96 * (120)/(20)`

`n =(1.96 * (120)/(20))^2`

`n =138.2976`

So, n = 138

Hence sample size should be 138 selected to obtain a .95 probability of estimating the population mean monthly income within a margin of $20