A study was recently conducted to estimate the mean cholesterol for adult males over the age of 55 years. From a random sample of n = 10 men, the sample mean was found to be 242.6 and the sample standard deviation was 73.33. To find the 95 percent confidence interval estimate for the mean, the correct critical value to use is:
A) 1.96
B) 2.2281
C) 2.33
D) 2.2622

Question

Quizplus · Accepted Answer

The correct critical value for a 95% confidence interval when the sample size is small (n < 30) and the population standard deviation is unknown is found using the t-distribution. The degrees of freedom (df) in this case is n - 1 = 10 - 1 = 9. Looking up the t-table for 9 degrees of freedom at a 95% confidence level gives a critical value of approximately 2.262.

A Study Was Recently Conducted to Estimate the Mean Cholesterol