I’m studying for my Statistics class and need an explanation.

Section 6.1 #38

Compute the mean and standard deviation of the random variable with the given discrete probability distribution.

38.	xP(x)1200.301500.301700.151800.25

and

Section 6.2 #38a

38. Big babies: The Centers for Disease Control and Prevention reports that 25% of baby boys 6–8 months old in the United States weigh more than 20 pounds. A sample of 16 babies is studied.

a. What is the probability that exactly 5 of them weigh more than 20 pounds?