Question

To estimate μ, the mean salary of full professors at American colleges and universities, you obtain the salaries of a random sample of 400 full professors. The sample mean is ¯x = $73,220 and the sample standard deviation is s = $4400. A 99% confidence interval for μ is:A.) 73220 ± 11440B.) 73220 ± 577C.) 73220 ± 431D.) 73220 ± 28.6

Answer 1

Answer:

73220±566.72

Step-by-step explanation:

The formula for calculating the confidence interval is expressed as;

CI = xbar ± z*s/√n

xbar is the sample mean =  $73,220

z is the z score at 99% CI = 2.576

s is the standard deviation = $4400

n is the sample size = 400

Substitute the given values into the formula;

CI = 73,220 ± 2.576*4400/√400

CI = 73,220 ± 2.576*4400/20

CI = 73,220± (2.576*220)

CI = 73220±566.72

Hence a 99% confidence interval for μ is 73220±566.72