Suppose the heights of 18-year-old men are approximately normally distributed, with mean 70 inches and standard deviation 4 inches. What is the probability that an 18-year-old man selected at random is between 69 and 71 inches tall? (Round your answer to four decimal places.)

I got 0.1974 as my answer. I cannot figure out the rest.

If a random sample of sixteen 18-year-old men is selected, what is the probability that the mean height x? is between 69 and 71 inches? (Round your answer to four decimal places.)

Compare your answers to parts (a) and (b). Is the probability in part (b) much higher? Why would you expect this?