So...I made a mistake and took a 4wk stats summer course. Completely bombed my quiz today. Can someone explain this to me? Answer is A, but why?

The proportion of American births that result in a birth defect is approximately 1/33 according to the Centers for Disease Control and Prevention (CDC). A local hospital randomly selects five births and lets the random variable X count the number not resulting in a defect. Assume the births are independent.

X follows a
A. binomial distribution with n = 5 and p = 1/33.
B. None of the above
C. Normal distribution with mean 5 and variance 1/33.

Question

So...I  made a mistake and took a 4wk stats summer course. Completely bombed my quiz today. Can someone explain this to me? Answer is A, but why?

The proportion of American births that result in a birth defect is approximately 1/33 according to the Centers for Disease Control and Prevention (CDC). A local hospital randomly selects five births and lets the random variable X count the number not resulting in a defect. Assume the births are independent.

X follows a
A.	binomial distribution with n = 5 and p = 1/33.
B.	None of the above
C.	Normal distribution with mean 5 and variance 1/33.

blockcolder · Answer

Characteristics of a binomial distribution:
1. There are only two results: success and failure. (ie, has defect and has no defect)
2. The trials are independent.