# 01 November 2013 • Name:

MonthWater
January 830
February 5560
March 11390
April 8330
May 5280
June 10010
July 5000
August 10560
September 10260
October 9790

The data is the gallons of water used in a home per month in 2013.

1. n = __________ Calculate the sample size n.
2. x = __________ Calculate the sample mean x.
3. sx = __________ Calculate the sample standard deviation sx.
4. SE = __________ Calculate the standard error SE.
5. tc = ____________________ Given a confidence level c = 0.95, calculate tcritical
6. E = _________ Calculate the margin of error E for the sample mean x.
7. Write out the 95% confidence interval for the possible population mean μ
p(_____________ < μ < ___________) = 0.95
8. _______________ In 2012 the home was averaging 12800 gallons per month at an average cost of \$30.34 per month. The family in the home committed to using less water per month in 2013. Is 12800 gallons a possible population mean for the sample data?
9. _______________ Did the home use statistically significantly less water per month in 2013 at a confidence level of 95%?

Given a null hypothesis of H0: μ = 12800
and the alternative hypothesis of H1: μ ≠ 12800
Run a hypothesis test at a risk of a type I error alpha α = 0.05
10. t = ____________________ Calculate the t-statistic t
11. p-value = ____________________ Use =tdist(abs(t),n−1,2) to calculate the p-value.
12. ____________________ Calculate the largest possible confidence interval which does not include 12800 by calculating 1 − p-value.
13. ____________________ Is the sample mean x statistically significantly different from the population mean μ of 12800?
14. _____________________ At an alpha α of 5%, would you fail to reject |or| reject the null hypothesis?
15. _______________ Is the home using less water in 2013 at an alpha of 5%?