Answer:
d. normal if the population is normally distributed
Explanation:
Central Limit Theorem
The Central Limit Theorem establishes that, for a normally distributed random variable X, with mean
and standard deviation
, the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean
and standard deviation
.
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
In this question:
Sample size less than 30, so only will be normal if the population is normally distribution, and thus the correct answer is given by option d.