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
Probability and Statistics for Engineering and the Sciences
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- Following are the protein contents measured in two types of species:Species 1: 0.72 1.12 0.81 0.89 0.72 0.81 1.01 0.75 0.83Species 2: 1.21 0.93 0.80 1.12 1.22 0.94 0.87 i) Assuming normality, test the hypothesis that the two species have the sameaverage protein contents by using 5-step hypothesis testing procedure at 5 %level of significance, and using the critical values approach.ii) Calculate the p-value of this test and make decision.iii) Write down the standard error of this test and calculate its numerical value ?arrow_forwardBased on her own experiences in court, a prosecutor believes that some judges provide more severe punishments than other judges for people convicted of domestic violence. Five of the most recent domestic violence sentences (in years) handed down by three judges are recorded below. Judge 1 Judge 2 Judge 3 1 3 3 1 2 5 3 4 5 2 3 6 2 4 4 Using this information, test the null hypothesis at the .05 level of significance that judges do not vary in the sentence lengths imposed on individuals convicted of domestic violence. In so doing, please: (1) identify the research and null hypotheses, (2) the critical value needed to reject the null, (3) the decision that you made upon analyzing the data, and (4) the conclusion you have drawn based on the decision you have made.arrow_forwardA heart study objective was to study heart disease among healthy volunteers.After a 10-year follow-up period involving men aged 40 to 59, there were 16 casesof coronary heart disease (CHD) among the 454 men who initially had cholesterollevels below 210 mg/100 ml (referred to as the low serum cholesterol group). Incontrast, among the 424 men whose initial cholesterol levels were at least 245mg/100 ml (referred to as the high serum cholesterol group), there were 51 cases ofCHD. With this information, Draw a 2x2 contingency table then calculate the relative risk (RR) associated with high serum cholesterol and provide an interpretation of the result.arrow_forward
- A study on the oxygen consumption rate (OCR) of sea cucumbers involved a random sample of size 12 at 15oC and a second random sample of size 5 kept at 18oC. To test the hypothesis that this range of temperature had no effect on the OCR, what is the degrees of freedom for a two-sample t-test?arrow_forwardA consumer group is investigating a producer of diet meals to examine if its prepackaged meals actually contain the advertised 6 ounces of protein in each package. Based on the following data, is there any evidence that the meals do not contain the advertised amount of protein? Run the appropriate test at a 5% level ofarrow_forwardIn a random sample of 85 automobile engine crankshaft bearings, 10 have a surface finishroughness that exceeds the specifications. Do these data present strong evidence that theproportion of crankshaft bearings exhibiting excess surface roughness exceeds 0.10?State and test the appropriate hypotheses using α = 0.05.arrow_forward
- Following is the rating of marketing aggressivity (X) and sales performance (Y) of 8 sales staffs in Glovis Co in the past year: Table Attached Question: What is the hypothesis of the study?arrow_forwardThe manufacturer of a spot remover claims that hisproduct removes 90 percent of all spots. If, in a random sample, only 174 of 200 spots were removed with the man-ufacturer’s product, test the null hypothesis θ = 0.90 against the alternative hypothesis θ < 0.90 at the 0.05level of significance.arrow_forwardA random sample of 125 monthly balances for holders of a particular credit card indicated that the sample skewness was 0.55 and the sample kurtosis was 2.77. Test the null hypothesis that the population distribution is normal.arrow_forward
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