Answer :
Answer:
(c) If we do not know the population standard deviation and must use the sample standard deviation
Explanation:
A t distribution is used for the inference about the population mean if the population standard deviation (sigma) is unknown. The sample standard deviation (s) is used instead.
The test statistic of a t distribution is given as (sample mean - population mean) ÷ (sample standard deviation ÷ sqrt(sample size))
The test statistic of a standard normal distribution is given as (sample mean - population mean) ÷ (population standard deviation ÷ sqrt(sample size))