Answer: d. if we do not know the population standard deviation and must use the sample standard deviation.
Step-by-step explanation:
We use t-distribution is quite similar to distribution of z-score .
The interpretation of t-scores and z-scores are same.
T- distribution is used when the data is not accurately normal and when the population standard deviation is unknown.
In the absence of population standard deviation , we use the standard deviation of the sample.
So , We use a t distribution for inference about a population mean instead of the standard Normal distribution if we do not know the population standard deviation and must use the sample standard deviation.
Hence, the correct option is : d. if we do not know the population standard deviation and must use the sample standard deviation.
