Doing a confidence interval:

a. Show work on how formula was applied.

b. Interpret the interval as a complete sentence.

Doing a hypothesis test:

a. Write down the null and alternative hypotheses as a complete sentence

b. Write down the calculator input and output values.

c. Write down conclusion as a complete sentence.

Exercise 1

In a sample of seven cars, each car was tested for nitrogen oxide emissions (in grams per mile) and the following results were obtained: 0.06, 0.11, 0.16, 0.15, 0.14, 0.08, 0.15 (based on data from the EPA).Assuming that this sample is representative of the cars in use, construct a 98% confidence interval estimate of the mean amount of nitrogen oxide emissions for all cars. Interpret this confidence interval in terms of the population.

Exercise 2

Because cardiac deaths appear to increase after heavy snowfalls, an experiment was designed to compare cardiac demands of snow shoveling to those using an electric snow thrower. Ten subjects cleared tracts of snow using both methods, and their maximum heart rates (beats per minute) were recorded during both observed activities. The following results were obtained:

Method Used	Mean Heart Rate (bpm)	SD Heart Rate (bpm)
Manual	175	15
Electric	124	18

Building a 95% confidence interval for each methodology, discuss which methodology increases the risk for cardiac death. Is this difference enough to make a valid claim? Why? Make sure to illustrate each confidence interval and interpret them to argue your reasoning.

(Based on data from "Cardiac Demands of Heavy Snow Shoveling," by Franklin et. al., Journal of the American Medical Association, Vol. 273, No. 11)

Exercise 3

A group of students randomly selected 40 people and measured the accuracy of their wristwatches, with positive errors representing watches that are ahead of the correct time and negative errors representing below the correct time. The students reported a sample mean error of +1 min. and 57 sec and a standard deviation of 3 min. and 5 sec. Using a 2% significance level, what can be concluded about the accuracy of the average person's wristwatch?

Exercise 4

An experiment is conducted to determine whether intensive tutoring (covering a great deal of material in a fixed amount of time) is more effective than paced tutoring (covering less material in the same amount of time). Two randomly chosen groups are tutored separately and then administered proficiency tests. The sample size of the intensive group is 10 with sample average 76 and sample SD 6; the sample size of the paced group is 12 with sample average 70 and sample SD 8. May we conclude that the intensive group is doing better?