A population has a standard deviation of 25. A random sample of 125 items from this population is selected. The sample mean is determined to be 325. At 95% confidence, the margin of error is
A) 2.24.
B) 5.
C) 4.38.
D) 11.18.

Question

Quizplus · Accepted Answer

The formula for the margin of error is:

Margin of error = Z* (standard deviation / square root of sample size)

Where Z* is the critical value for the desired level of confidence, which is 1.96 for 95% confidence.

Plugging in the values, we get:

Margin of error = 1.96 * (25 / sqrt(125))

= 1.96 * 2.236

= 4.38

Therefore, the margin of error at 95% confidence is 4.38 (choice C).

A Population Has a Standard Deviation of 25