Question

The monthly incomes from a random sample of workers in a factory are shown below.

Monthly Income, in $1,000
4.0
5.0
7.0
5.0
6.0
6.0
10.0
8.0
9.0

(Please, avoid rounding intermediate steps and round your final solutions to at least 2 decimal places)

Compute the 95% confidence interval for the mean monthly incomes of the workers. Provide the lower and upper bound of the interval below and give your answer in dollars.

Are there any additional assumptions needed in this problem to ensure that computed confidence interval is reliable?

A. Yes, the population needs to be normally distributed because the sample is too small to apply CLT.

B. No additional assumptions needed.

C. Yes, population standard deviation should be known.

D. Yes, the sample size has to be increased. With the current sample size the confidence interval cannot be reliable.