Final answer:
The sample size for xbar doesn't have to be greater than 30 if the samples are normally distributed, symmetrically distributed, or skewedly distributed.
Step-by-step explanation:
The correct answer is D. All of the above. The sample size for xbar doesn't have to be greater than 30 if the samples are normally distributed, symmetrically distributed, or skewedly distributed. In such cases, the central limit theorem states that as the sample size increases, the sampling distribution of the sample mean approaches a normal distribution, regardless of the shape of the population distribution.