3.The Average Mpg Usage for a 2004 Ford Expedition 2WD for a Sample of 10 Tanks of Gas Was 17.0

1. Describe what a Chi-Square test does. When would you use it and give an example.

2.We introduced the concept of an intervention – an event that causes our data to change in a “Before” and “After” comparison sense. Both ANOVA and Chi-Square can tell us if there is a difference between samples of similar populations – ANOVA for comparing 3 or more like samples, Chi-Square between an observed and expected outcome. Explain how you as a manager might use either of these tools to see if you need to change what you are doing – i.e., increase training, modify operating procedures, etc.

3.The average mpg usage for a 2004 Ford Expedition 2WD for a sample of 10 tanks of gas was 17.0

with a standard deviation of 0.8. For a Ford Explorer 2WD, the average mpg usage for a sample of

10 tanks of gas was 18.5 with a standard deviation of 1.0. (a) Assuming equal variances, at

α = .01, is the true mean mpg lower for the Ford Expedition? (b) Calculate the p-value using

Excel. (Data are from

N1=30 N2=40

Formula

4. A new cell phone battery is being considered as a replacement for the current one. Ten college

student cell phone users are selected to try each battery in their usual mix of “talk” and “standby”

and to record the number of hours until recharge was needed. (a) Do these results show that the

new battery has significantly longer life at α = .05? State your hypotheses and show all steps

clearly. (b) Is the decision close? (c) Are you convinced?

10.

Excel’s independent sample t tests

Bob May Deno Sri Pat Alexis Scott Aretha Jen Ben

New battery 45 41 53 40 43 43 49 39 41 43

Old battery 52 34 40 38 38 44 34 45 28 33

Formula

5. To test the hypothesis that students who finish an exam first get better grades, Professor Hardtack

kept track of the order in which papers were handed in. The first 25 papers showed a mean score of

77.1 with a standard deviation of 19.6, while the last 24 papers handed in showed a mean score of

69.3 with a standard deviation of 24.9. Is this a significant difference at α = .05? (a) State the

hypotheses for a right-tailed test. (b) Obtain a test statistic and p-value assuming equal variances.

Interpret these results. (c) Is the difference in mean scores large enough to be important? (d) Is it reasonableto assume equal variances? (e) Carry out a formal test for equal variances at α = .05, showing

all steps clearly.

Formulas

6.Team B: Use the RES 342 Equation Helper (Chi Square tab) OR The “Chi Square Goodness of Fit” file (both in the Week 3 course materials) for this problem:The publisher of a sports magazine plans to offer new subscribers one of three gifts: a sweatshirt with the logo of their favorite team, a coffee cup with the logo of their favorite team, or a pair of earrings also with the logo of their favorite team. In a sample of 500 new subscribers, the number selecting each gift is reported below. At the .05 significance level, is there a preference for the gifts or should we conclude that the gifts are equally well liked?