A random sample of size 15 taken from a normally distributed population revealed a sample mean of 75 and a sample variance of 25.The upper limit of a 95% confidence interval for the population mean would equal:
A) 77.769.
B) 72.231.
C) 72.727.
D) 77.273.

Question

Quizplus · Accepted Answer

The upper limit of a 95% confidence interval for the population mean is calculated using the formula: mean + (t-value * standard error). The standard error is the square root of the variance divided by the sample size. With a sample size of 15, degrees of freedom are 14. The t-value for 95% confidence and 14 degrees of freedom is approximately 2.145. Thus, the upper limit is 75 + (2.145 * sqrt(25/15)) = 77.769.

A Random Sample of Size 15 Taken from a Normally