A study of 75 apple trees showed that the average number of apples per tree was 925. The standard deviation of the population is 100. Which of the following is the 95% confidence interval for the mean number of apples per tree for all trees?

Question

Quizplus · Accepted Answer

We can use the formula: 
confidence interval = sample mean ± (z-value x standard error)

We don't have the sample standard deviation, so we'll use the population standard deviation as an estimate.

The standard error = standard deviation / sqrt(sample size) = 100 / sqrt(75) = 11.547

Using a 95% confidence level, the z-value is 1.96.

Plugging in the values: 
confidence interval = 925 ± (1.96 x 11.547) = (902.98, 947.02)

Therefore, the best choice is C.

A Study of 75 Apple Trees Showed That the Average