1). A class survey in a large class for first-year college students asked, "About how many hours do you study in a typical week?". The mean response of the 432 students was x¯¯¯ = 15 hours. Suppose that we know that the study time follows a Normal distribution with standard deviation 8 hours in the population of all first-year students at this university.

What is the 99% confidence interval (±0.001) for the population mean?

Confidence interval is from _ to _ hours.

2). We have the survey data on the body mass index (BMI) of 650 young women. The mean BMI in the sample was x¯¯¯=26.5. We treated these data as an SRS from a Normally distributed population with standard deviation σ=7.

Find the margins of error for 99% confidence based on SRSs of N young women.

N margins of error (±0.0001)

106 ?

380 ?

1597 ?