Consider the following statements concerning confidence

Question

Consider the following statements concerning confidence interval estimates:

A. The use of the pooled variance estimator when constructing a confidence interval for the difference between means requires the assumption that the population variances are equal.

B. The width of a confidence interval estimate for the proportion, or for mean when the population standard deviation is known, is inversely proportional to the square root of the sample size.

C. To determine the sample size required to achieve a desired precision in the confidence interval estimate for the mean, the critical value for the standard normal distribution (ie. Z value) is required.

1. only A is true
2. only A and B are true
3. only A and C are true
4. only B and C are true
5. A, B and C are true

Which is correct?