Question

What is the lower bound of a 95% confidence interval with a sample mean of 22, population standard deviation of 10, and sample size of 40.

Question 1 options:

A. 12

B.18.90

C. 25.10

D. 22

Answer 1

As per the provided information,

The population standard deviation is 10.

The sample size (n) is 40.

The sample mean is 22.

The confidence level (c) is 0.95, so the significance level is 0.05 (= 1 – 0.05).

The two tailed critical value obtained from the z-table at the 0.05 alpha (significance level) is +/- 1.96.

The lower bound of a 95% confidence interval for the population mean is given by,

Therefore, the lower bound of a 95% confidence interval for the population mean is 18.90.

Hence, the option B is correct.