## (solution) This is for a statistics class and I have to show work.

This is for a statistics class and I have to show work.

Problem Solving Assignment - Week 5

Chapter 8 - Exercises: 2, 4, 8

2. The producers of a new toothpaste claim that it prevents more cavities than other brands of

toothpaste. A random sample of 60 people used the new toothpaste for 6 months. The mean

number of cavities at their next checkup is 1.5. In the general population, the mean number of

cavities at a 6-month checkup is 1.73 (? = 1.12). a. Is this a one- or two-tailed test?

b. What are H0 and Ha for this study?

c. Compute zobt.

d. What is zcv?

e. Should H0 be rejected? What should the researcher conclude?

f. Determine the 95% confidence interval for the population mean, based on the sample mean. 4. Henry performed a two-tailed test for an experiment in which N = 24. He could not find his

table of t critical values, but he remembered the tcv at df = 13. He decided to compare his tobt with

this tcv. Is he more likely to make a Type I or a Type II error in this situation? 8. A researcher believes that the percentage of people who exercise in California is greater than

the national exercise rate. The national rate is 20%. The researcher gathers a random sample of

120 individuals who live in California and finds that the number who exercise regularly is 31 out

of 120. a. What is ?2obt?

b. What is df for this test?

c. What is ?2cv?

d. What conclusion should be drawn from these results?

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