Answer:
The sampling distribution of X is centered at 15cm and the standard deviation of the X distribution is 0.0125cm.
Step-by-step explanation:
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean
and standard deviation
, the sample means with size n can be approximated to a normal distribution with mean
and standard deviation 
(a) If X is the sample mean diameter for a random sample of n = 16 rings, where is the sampling distribution of X centered and what is the standard deviation of the X distribution?
Mean: 
Standard deviation:

The sampling distribution of X is centered at 15cm and the standard deviation of the X distribution is 0.0125cm.