Question

To estimate the average students' scores in a standardize test, a sample of 22 scores yielded a mean of 70 and a standard deviation of 10. What is a lower limit for a 99% confidence interval for the population mean?

Answer 1

Formula for lower limit of confidence interval for the population mean:

for 99% confidence level =(100-99)/100=0.01

/2 = 0.01/2 = 0.005

Given,

Sample size : n = 22

Sample mean : =70

Sample standard deviation : s = 10

Degrees of freedom = n-1=22-1=21

lower limit of 99% confidence interval for the population mean:

lower limit of 99% confidence interval for the population mean: 63.9634