Concept explainers
According to the article “Fatigue Testing of Condoms” (Polymer Testing, 2009: 567–571), “tests currently used for condoms are surrogates for the challenges they face in use,” including a test for holes, an inflation test, a package seal test, and tests of dimensions and lubricant quality (all fertile territory for the use of statistical methodology!). The investigators developed a new test that adds cyclic strain to a level well below breakage and determines the number of cycles to break. A sample of 20 condoms of one particular type resulted in a sample mean number of 1584 and a sample standard deviation of 607. Calculate and interpret a confidence interval at the 99% confidence level for the true average number of cycles to break. [Note: The article presented the results of hypothesis tests based on the t distribution; the validity of these depends on assuming
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Chapter 7 Solutions
Student Solutions Manual for Devore's Probability and Statistics for Engineering and the Sciences, 9th
- The authors of the paper "Statistical Methods for Assessing Agreement Between Two Methods of Clinical Measurement" compared two different instruments for measuring a subject's ability to breathe out air.† (This measurement is helpful in diagnosing various lung disorders.) The two instruments considered were a Wright peak flow meter and a mini-Wright peak flow meter. Seventeen subjects participated in the study, and for each subject air flow was measured once using the Wright meter and once using the mini-Wright meter. Subject 1 2 3 4 5 6 7 8 9 Mini- Wright Meter 512 430 520 428 500 600 364 380 658 Wright Meter + 494 395 516 434 476 557 413 442 650 Subject 10 11 12 13 14 15 16 17 Mini- Wright Meter 445 432 626 260 477 259 350 451 Wright Meter 433 417 656 267 478 178 423 427 (a) Suppose that the Wright meter is considered to provide a better measure of air flow, but the mini-Wright meter is easier to transport and to use. If the two types of meters produce different readings but there is…arrow_forward2. A manufacturer of construction materials claims that their structural steel rods have a mean tensile strength of 500Mpa. We test a sample of 9 of the rods for their tensile strength (in MPa) and record the results below. 494 491 477 485 493 507 474 493 508 From our sample, is there evidence to suggest that the true mean tensile strength of the rods is not 500 Mpa? Perform the appropriate hypothesis test. (a) Using the correct notation, define the parameter of interest. Then, state the null and alternative hypotheses for this study in terms of the parameter. (b) Specify (with justification) the test statistic and state its distribution (Z or T, and degrees of freedom, if needed) it follows. (c) Compute the observed value of the test statistic. (d) Compute the p-value or provide a range of appropriate values for the p-value. (e) Using the p-value, determine the level of evidence against Ho. In a plain English sentence, state a conclusion for the study. 2arrow_forward4) Please provide a correct answer with a full method explanation and do not copy and past from other similar questions.arrow_forward
- 3. According to the study of Fitbit, a company producing fitness trackers, women typically have higher resting heart rates. Use the R commander output below to test if the same result applies to Dr. Castillejo's gym members. Write a brief report about the analysis by identifying the set of hypotheses to be tested, the appropriate test to use, and implications and recommendations of/from the conclusions. R COMMANDER OUTPUT R COMMANDER OUTPUT data: Shapiro-Wilk normality test reatulas male Shapiro-Wilk normality test data: reapulae female W = 0.94898, p-value = 0.17212 W = 0.96948, p-value = 0.72155 R COMMANDER OUTPUT F test to compare two variances data: seateulae male and restrulae female F = 1.3110, num df = 20, denom di = 28, p-value = 0.5002 Alternative hypothesis: true ratio of variances is not equal to 1 R COMMANDER OUTPUT parametric test. data: Fetulae female and restulae male (Female Male) t = 0.94747, df = 48, p-value = 0.174123 alternative hypothesis: true difference in means…arrow_forwardYou may need to use the appropriate appendix table or technology to answer this question. An agency reports that 11.7% of workers in a particular country belonged to unions. Suppose a sample of 300 workers is collected to determine whether union efforts to organize have increased union membership. (a) Formulate the hypotheses that can be used to determine whether union membership has increased. H0: p = 0.117 Ha: p ≠ 0.117 H0: p ≥ 0.117 Ha: p < 0.117 H0: p ≤ 0.117 Ha: p > 0.117 H0: p < 0.117 Ha: p ≥ 0.117 H0: p > 0.117 Ha: p ≤ 0.117 (b) If the sample results show that 42 of the workers belonged to unions, what is the p-value for your hypothesis test? Find the value of the test statistic. (Round your answer to two decimal places.) Find the p-value. (Round your answer to four decimal places.) p-value =arrow_forwardYou may need to use the appropriate appendix table or technology to answer this question. An agency reports that historically 11.3% of workers in a particular country belong to unions. Suppose a sample of 300 workers is collected to determine whether union efforts to organize have increased union membership. (a) Formulate the hypotheses that can be used to determine whether union membership has increased. H0: p ≥ 0.113 Ha: p < 0.113 H0: p = 0.113 Ha: p ≠ 0.113 H0: p ≤ 0.113 Ha: p > 0.113 H0: p < 0.113 Ha: p ≥ 0.113 H0: p > 0.113 Ha: p ≤ 0.113 (b) If the sample results show that 36 of the workers belonged to unions, what is the p-value for your hypothesis test? Find the value of the test statistic. (Round your answer to two decimal places.) Find the p-value. (Round your answer to four decimal places.) p-value = (c) At α = 0.05, what is your conclusion? Reject H0. There is insufficient evidence to conclude that there has been an increase in union…arrow_forward
- You may need to use the appropriate appendix table or technology to answer this question. An agency reports that 11.5% of workers in a particular country belonged to unions. Suppose a sample of 300 workers is collected to determine whether union efforts to organize have increased union membership. (a) Formulate the hypotheses that can be used to determine whether union membership has increased. H0: p ≥ 0.115 Ha: p < 0.115 H0: p ≤ 0.115 Ha: p > 0.115 H0: p = 0.115 Ha: p ≠ 0.115 H0: p > 0.115 Ha: p ≤ 0.115 H0: p < 0.115 Ha: p ≥ 0.115 (b) If the sample results show that 36 of the workers belonged to unions, what is the p-value for your hypothesis test? Find the value of the test statistic. (Round your answer to two decimal places.) Find the p-value. (Round your answer to four decimal places.) p-value = (c) At ? = 0.05, what is your conclusion? Reject H0. There is insufficient evidence to conclude that there has been an increase in union…arrow_forward3. Which of the following problem statements indicate the use of a double-sided hypothesis test? A. Suppose that a fabric is unsuitable for dyeing if its water pickup is less than 55%. Is the cotton fabric under consideration suitable for dyeing? B. A supplier claims that its products made from a graphite-epoxy composite material have a tensile strength of 40. An experimenter may test this claim by collecting a random sample of products and measuring their tensile strengths. C. A manufacturer claims that its cars achieve an average of at least 35 miles per gallon in highway driving. A consumer interest group tests this claim by driving a random selection of the cars in highway conditions and measuring their fuel efficiency. D. Suppose we are interested in the average online exposure time of students, a random variable that can be described by a probability distribution. We are interested in deciding whether or not the mean exposure time is now greater than lower than 8 hours per day…arrow_forwardRegulations from the Environmental Protection Agency say that soil used in play areas should not have lead levels that exceed a 400 parts per million (ppm). Before beginning construction at a new site, an agent will take a sample of soil and run a significance test on the mean lead level in the soil. If the mean lead level in the sample is significantly higher than 400 ppm, then the soil is deemed unsafe and construction cannot continue. Here are the hypotheses for this test: Ho : µ 400 ppm (soil is unsafe) (where u is the mean lead level in the soil at the new site). Which of the following would be a Type I error in this setting? Choose 1 answer: The soil is actually safe, and the sample result is below 400 ppm. so construction continues. The soil is actually safe, and the sample result is significantly higher than 400 ppm. so construction stops. The soil is actually unsafe, and the sample result is below 400 ppm, so construction continues. The soil is actually unsafe, and the sample…arrow_forward
- Regulations from the Environmental Protection Agency say that soil used in play areas should not have lead levels that exceed a 400 parts per million (ppm). Before beginning construction at a new site, an agent will take a sample of soil and run a significance test on the mean lead level in the soil. If the mean lead level in the sample is significantly higher than 400 ppm, then the soil is deemed unsafe and construction cannot continue. Here are the hypotheses for this test: Ho : µ 400 ppm (soil is unsafe) (where u is the mean lead level in the soil at the new site). Which of the following would be a Type I error in this setting?arrow_forwardYou may need to use the appropriate appendix table or technology to answer this question. An agency reports that 11.5% of workers in a particular country belonged to unions. Suppose a sample of 300 workers is collected to determine whether union efforts to organize have increased union membership. (a) Formulate the hypotheses that can be used to determine whether union membership has increased. H0: p = 0.115 Ha: p ≠ 0.115 H0: p > 0.115 Ha: p ≤ 0.115 H0: p ≤ 0.115 Ha: p > 0.115 H0: p ≥ 0.115 Ha: p < 0.115 H0: p < 0.115 Ha: p ≥ 0.115 (b) If the sample results show that 42 of the workers belonged to unions, what is the p-value for your hypothesis test? Find the value of the test statistic. (Round your answer to two decimal places.) Find the p-value. (Round your answer to four decimal places.) p-value = (c) At ? = 0.05, what is your conclusion? - Reject H0. There is sufficient evidence to conclude that there has been an increase in union membership. -…arrow_forwardYou may need to use the appropriate appendix table or technology to answer this question. An agency reports that 11.5% of workers in a particular country belonged to unions. Suppose a sample of 300 workers is collected to determine whether union efforts to organize have increased union membership. (a) Formulate the hypotheses that can be used to determine whether union membership has increased. H0: p = 0.115 Ha: p ≠ 0.115 H0: p > 0.115 Ha: p ≤ 0.115 H0: p ≤ 0.115 Ha: p > 0.115 H0: p ≥ 0.115 Ha: p < 0.115 H0: p < 0.115 Ha: p ≥ 0.115 (b) If the sample results show that 36 of the workers belonged to unions, what is the p-value for your hypothesis test? Find the value of the test statistic. (Round your answer to two decimal places.) Find the p-value. (Round your answer to four decimal places.) p-value = (c) At ? = 0.05, what is your conclusion? Do not reject H0. There is insufficient evidence to conclude that there has been an increase in union…arrow_forward
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