When finding a confidence interval for a population mean based on a sample of size 11, which assumption is made?

Question

The standard deviation is fixed.

The sampling distribution of z is normal.

The sampling distribution of the sample means is approximately normal.

There is no special assumption made.

I would think D, no special assumption.

Answer 1

I would also say D. If a problem does not say "assuming a normal distribution" in its statement, then one can use the t-distribution instead for smaller sample sizes (less than 30).