In Exercises 1–5, use the following survey results: Randomly selected subjects were asked if they were aware that the Earth has lost half of its wildlife population during the past 50 years. Among 1121 women, 23% said that they were aware. Among 1084 men, 26% said that they were aware (based on data from a Harris poll).

Biodiversity Find the values of \({x_1}\)(the number of women who were aware of the statement), \({x_2}\) (the number of men who were aware of the statement),\({\hat p_1}\), \({\hat p_2}\)and the pooled proportion \(\bar p\)obtained when testing the claim given in Exercise 1.

Short Answer

Expert verified

The value of \({x_1}\) is equal to 258.

The value of \({x_2}\) is equal to 282.

The value of \({\hat p_1}\) is equal to 0.23.

The value of \({\hat p_2}\) is equal to 0.26.

The value of \(\bar p\) is equal to 0.245.

Step by step solution

01

Given information

In a sample of 1121 women, 23% said that they were aware of the fact that the Earth has lost half of its wildlife population during the past 50 years. In another sample of 1084 men, 26% said that they were aware that the Earth had lost half of its wildlife population during the past 50 years.

02

Values of \({x_1}\) and \({x_2}\)

It is given that\({x_1}\)is the number of women who were about the fact.

Thus, the value of\({x_1}\)is computed below:

\(\begin{array}{c}{x_1} = 23\% \;{\rm{of}}\;1121\\ = \frac{{23}}{{100}} \times 1121\\ \approx 258\end{array}\)

Thus, the value of\({x_1}\)is equal to 258.

Similarly,

It is given that\({x_2}\)is the number of men who were about the fact.

Thus, the value of\({x_2}\)is computed below:

\(\begin{array}{c}{x_2} = 26\% \;{\rm{of}}\;1084\\ = \frac{{26}}{{100}} \times 1084\\ \approx 282\end{array}\)

Thus, the value of \({x_2}\) is equal to 282.

03

Values of \({\hat p_1}\) and \({\hat p_2}\)

Let\({\hat p_1}\)denote the sample proportion of women who were about the stated fact.

It is given that out of 1121 women, 23% said that they were aware of the fact.

Thus,\({\hat p_1}\)is equal to:

\(\begin{array}{c}{{\hat p}_1} = 23\% \\ = \frac{{23}}{{100}}\\ = 0.23\end{array}\)

Therefore, the value of\({\hat p_1}\)is equal to 0.23.

Let\({\hat p_2}\)denote the sample proportion of men who were about the stated fact.

It is given that out of 1084 men, 26% said that they were aware of the fact.

Thus,\({\hat p_2}\)is equal to:

\(\begin{array}{c}{{\hat p}_1} = 26\% \\ = \frac{{26}}{{100}}\\ = 0.26\end{array}\)

Therefore, the value of \({\hat p_2}\) is equal to 0.26.

04

Value of \(\bar p\)

Let\({n_1}\)denote the sample size corresponding to women.

\({n_1}\)is equal to 1121.

Let\({n_2}\)denote the sample size corresponding to men.

\({n_2}\)is equal to 1084.

The value of the pooled proportion is equal to:

\(\begin{array}{c}\bar p = \frac{{\left( {{x_1} + {x_2}} \right)}}{{\left( {{n_1} + {n_2}} \right)}}\\ = \frac{{\left( {258 + 282} \right)}}{{\left( {1121 + 1084} \right)}}\\ = 0.245\end{array}\)

Thus, the value of \(\bar p\) is equal to 0.245.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

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.

Is Echinacea Effective for Colds? Rhinoviruses typically cause common colds. In a test of the effectiveness of Echinacea, 40 of the 45 subjects treated with Echinacea developed rhinovirus infections. In a placebo group, 88 of the 103 subjects developed rhinovirus infections (based on data from “An Evaluation of Echinacea Angustifolia in Experimental Rhinovirus Infections,” by Turner et al., New England Journal of Medicine, Vol. 353, No. 4). We want to use a 0.05 significance level to test the claim that Echinacea has an effect on rhinovirus infections.

a. Test the claim using a hypothesis test.

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

c. Based on the results, does Echinacea appear to have any effect on the infection rate?

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?

Red Background n = 35, x = 15.89, s = 5.90

Blue Background n = 36, x = 12.31, s = 5.48

In Exercises 5–20, assume that the two samples are independent random samples selected from normally distributed populations. 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).

Are male and female professors rated differently? According to Data Set 17 “Course Evaluations” Appendix B, given below are student evaluation scores of female professors and male professors. The test claims that female and male professors have the same mean evaluation ratings. Does there appear to be a difference?

Females

4.4

3.4

4.8

2.9

4.4

4.9

3.5

3.7

3.4

4.8

Males

4.0

3.6

4.1

4.1

3.5

4.6

4.0

4.3

4.5

4.3

Independent and Dependent Samples Which of the following involve independent samples?

a. Data Set 14 “Oscar Winner Age” in Appendix B includes pairs of ages of actresses and actors at the times that they won Oscars for Best Actress and Best Actor categories. The pair of ages of the winners is listed for each year, and each pair consists of ages matched according to the year that the Oscars were won.

b. Data Set 15 “Presidents” in Appendix B includes heights of elected presidents along with the heights of their main opponents. The pair of heights is listed for each election.

c. Data Set 26 “Cola Weights and Volumes” in Appendix B includes the volumes of the contents in 36 cans of regular Coke and the volumes of the contents in 36 cans of regular Pepsi.

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.

License Plate Laws The Chapter Problem involved passenger cars in Connecticut and passenger cars in New York, but here we consider passenger cars and commercial trucks. Among2049 Connecticut passenger cars, 239 had only rear license plates. Among 334 Connecticuttrucks, 45 had only rear license plates (based on samples collected by the author). A reasonable hypothesis is that passenger car owners violate license plate laws at a higher rate than owners of commercial trucks. Use a 0.05 significance level to test that hypothesis.

a. Test the claim using a hypothesis test.

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

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free