Question

Some people say that more babies are born in september than in any other month. to test this claim, you take a simple random sample of 150 students at your school and find that 21 of them were born in september. you are interested in whether the proportion born in september is higher than 1/12—what you would expect if september was no different from any other month.

Answer 1

Answer: Yes, 21 is higher than what you would expect if September was like any other month.

There are 12 months in the years. If all months were equally likely, then they would each have 1/12 of the babies.

1/12 of 150 is 12.5. The expected number of babies per month would be 12.5.

However, in the sample, there were 21 babies in September.