What is the key word(s) in the below which indicate that the "Population Mean" is known in the below? (In short what word makes this suitable to use the Z score instead of the T Score), as is the Standard Deviation of 12 not for the Sample?
Suppose a random sample of 36 is selected from a population with a standard deviation of 12. If the sample mean is 98, the 99% confidence interval for population mean is?