The head of a business school claims that the average MBA graduate is offered a starting salary of $55,000. The standard deviation of the offers is $4,600.

a) What is the probability that in a random sample of 38 MBA graduates, the mean starting salary is less than $53,000?

I am saying that

b) What if only 16 students had been sampled?

This is confusing, can I say

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as is known, can be used for ?