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