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

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 t-value for 14 degrees of freedom at 95% confidence is approximately 2.145. The standard error is the square root of the variance divided by the sample size, which is sqrt(25/15). Thus, the upper limit is 75 + (2.145 * sqrt(25/15)) = 77.769.

A Random Sample of Size 15 Taken from a Normally