An investigator conducts a study to investigate whether there is a difference in mean peak expiratory flow (PEF) in children with chronic bronchitis as compared to those without. Data on PEF are...

An investigator conducts a study to investigate whether there is a difference in mean peak expiratory flow (PEF) in children with chronic bronchitis as compared to those without.  Data on PEF are collected and summarized below.

1. Construct a 95% confidence interval for the mean PEF in children without chronic bronchitis.

b.
How many children would be required to ensure that the margin of error in (a) does not exceed 10 units? What is the margin of error?