Your Name: ____________________
Pledged: _______________________________________________________________
Math 140: Statistics, April 22, 2008
Quiz 16, Chapter 23: Accuracy of Averages
1. (8 pts.) In a hypothetical survey of families in a small city, a simple random sample of
900 families found that the average income of the families in the sample was $52,000
per year with an SD of $18,000.
a) Estimate the average income in the city as a give-or-take number.
b) 99.7%-confidence interval for the average income in the city.
2. (8 pts.) Twenty-five random draws will be made with replacement from the box
a) Give the average as a give-or-take number.
b) Estimate the chance that the average will be more than 2.2.
1
2
3