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In Exercises 5–16, use the listed paired sample data, and assume that the samples are simple random samples and that the differences have a distribution that is approximately normal.

Speed DatingAttributes Listed below are “attribute” ratings made by participants in a speed dating session. Each attribute rating is the sum of the ratings of five attributes (sincerity, intelligence, fun, ambition, shared interests). The listed ratings are from Data Set 18 “Speed Dating” in Appendix B. Use a 0.05 significance level to test the claim that there is a difference between female attribute ratings and male attribute ratings.

Rating of Male by Female

29

38

36

37

30

34

35

23

43

Rating of Female by Male

36

34

34

33

31

17

31

30

42

Short Answer

Expert verified

There is not sufficient evidence to support the claim that there is a significant difference between female attribute ratings and male attribute ratings.

Step by step solution

01

Given information

The attribute ratings given by participants in a speed dating session are provided.

It is claimed that there is a difference between male attribute ratings and female attribute ratings.

02

Defining the hypotheses

Null Hypothesis: The mean of the differences between male and female attribute ratings is equal to 0.

\({H_0}:{\mu _d} = 0\)

Alternative Hypothesis: The mean of the differences between male and female attribute ratings is not equal to 0.

\({H_1}:{\mu _d} \ne 0\)

03

Compute the mean and standard deviation of the differences

The differences between male and female attribute ratings are tabulated below:

Rating of Male by Female

29

38

36

37

30

34

35

23

43

Rating of Female by Male

36

34

34

33

31

17

31

30

42

Difference (d)

-7

4

2

4

-1

17

4

-7

1

The mean of the differences is computed below:

\(\begin{array}{c}\overline d = \frac{{\sum\limits_{i = 1}^n {{d_i}} }}{n}\\ = \frac{{\left( { - 7} \right) + 4 + ...... + 1}}{9}\\ = 1.89\end{array}\)

The standard deviation of the differences is computed below:

\(\begin{array}{c}{s_d} = \sqrt {\frac{{\sum\limits_{i = 1}^n {{{({d_i} - \overline d )}^2}} }}{{n - 1}}} \\ = \sqrt {\frac{{{{\left( {\left( { - 7} \right) - 1.89} \right)}^2} + {{\left( {4 - 1.89} \right)}^2} + ....... + {{\left( {1 - 1.89} \right)}^2}}}{{9 - 1}}} \\ = 7.15\end{array}\)

Thus, the mean and the standard deviation of the differences are 1.89 and 7.15, respectively.

04

Compute the test statistic

The assumption from the null hypothesis states that \({\mu _d} = 0\).

Then, the test statistic value is computed below:

\(\begin{array}{c}t = \frac{{\overline d - {\mu _d}}}{{\frac{{{s_d}}}{{\sqrt n }}}}\\ = \frac{{1.89 - 0}}{{\frac{{7.15}}{{\sqrt 9 }}}}\\ = 0.793\end{array}\)

Thus, the value of t is equal to 0.793.

05

State the critical values and the p-value

The value of the degrees of freedom is computed below:

\(\begin{array}{c}df = n - 1\\ = 9 - 1\\ = 8\end{array}\)

Using the t-distribution table, the critical values oft for 8 degrees of freedom and at a 0.05 level of significance are -2.306 and 2.306.

The two-tailed p-value of the z-score equal to 0.739 is equal to 0.4810.

06

Conclusion

Since the test statistic value lies within the two critical values and the p-value is greater than 0.05, the null hypothesis is failed to reject.

There is insufficient evidence to support the claim that there is a difference between female attribute ratings and male attribute ratings.

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Most popular questions from this chapter

Determining Sample Size The sample size needed to estimate the difference between two population proportions to within a margin of error E with a confidence level of 1 - a can be found by using the following expression:

E=zα2p1q1n1+p2q2n2

Replace n1andn2 by n in the preceding formula (assuming that both samples have the same size) and replace each of role="math" localid="1649424190272" p1,q1,p2andq2by 0.5 (because their values are not known). Solving for n results in this expression:

n=zα222E2

Use this expression to find the size of each sample if you want to estimate the difference between the proportions of men and women who own smartphones. Assume that you want 95% confidence that your error is no more than 0.03.

Verifying requirements in the largest clinical trial ever conducted, 401,974 children were randomly assigned to two groups. The treatment group considered of 201,229 children given the sulk vaccine for polio, and 33 of those children developed polio. The other 200,745 children were given a placebo, and 115 of those children developed polio. If we want to use the methods of this section to test the claim that the rate of polio is less for children given the sulk vaccine, are the requirements for a hypothesis test satisfied? Explain.

In Exercises 5–20, assume that the two samples are independent simple random samples selected from normally distributed populations, and do not assume that the population standard deviations are equal. (Note: Answers in Appendix D include technology answers based on Formula 9-1 along with “Table” answers based on Table A-3 with df equal to the smaller of n1−1 and n2−1.)Color and Cognition Researchers from the University of British Columbia conducted a study to investigate the effects of color on cognitive tasks. Words were displayed on a computer screen with background colors of red and blue. Results from scores on a test of word recall are given below. Higher scores correspond to greater word recall.

a. Use a 0.05 significance level to test the claim that the samples are from populations with the same mean.

b. Construct a confidence interval appropriate for the hypothesis test in part (a). What is it about the confidence interval that causes us to reach the same conclusion from part (a)?

c. Does the background color appear to have an effect on word recall scores? If so, which color appears to be associated with higher word memory recall scores?

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Before/After Treatment Results Captopril is a drug designed to lower systolic blood pressure. When subjects were treated with this drug, their systolic blood pressure readings (in mm Hg) were measured before and after the drug was taken. Results are given in the accompanying table (based on data from “Essential Hypertension: Effect of an Oral Inhibitor of Angiotensin-Converting Enzyme,” by MacGregor et al., British Medical Journal, Vol. 2). Using a 0.01 significance level, is there sufficient evidence to support the claim that captopril is effective in lowering systolic blood pressure?

Subject

A

B

C

D

E

F

G

H

I

J

K

L

Before

200

174

198

170

179

182

193

209

185

155

169

210

After

191

170

177

167

159

151

176

183

159

145

146

177

Testing Claims About Proportions. In Exercises 7–22, test the given claim. Identify the null hypothesis, alternative hypothesis, test statistic, P-value or critical value(s), then state the conclusion about the null hypothesis, as well as the final conclusion that addresses the original claim.

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a. Test the claim using a hypothesis test.

b. Test the claim by constructing an appropriate confidence interval.

c. Based on the results, does it appear that for in-hospital patients who suffer cardiac arrest, the survival rate is the same for day and night?

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