7.1-11. The heart rates (in beats per minute) of 41 ran- domly selected finishers of the Chicago Marathon, five minutes after they completed the race, had sample mean = 132 and sample variance s2 = 105. Assuming that the heart rates of all finishers of the Chicago Marathon five minutes after completing the race are normally dis-
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- Five samples of a ferrous-type substance were used to determine if there is a difference between a laboratory chemical analysis and an X-ray fluorescence analysis of the iron content. Each sample was split into two subsamples and the two types of analysis were applied, with the accompanying results. Assuming that the populations are normal, test at the 0.02 level of significance whether the two methods of analysis give, on the average, the same result. Click here to view the sample analyses. Click here to view page 1 of the table of critical values of the t-distribution. Click here to view page 2 of the table of critical values of the t-distribution. Let sample 1 be the X-ray fluorescence results and let sample 2 be the laboratory chemical results. State the null and alternative hypotheses. Ho: HD H1: HD + Identify the critical region. Select the correct choice below and fill in the answer box(es) to complete your choice. (Round to three decimal places as needed.) O A. t> В. t O C. t<Following an oil spill, a particular region of the ocean is being tested for the level of a chemical called naphthalene. It is considered fact that fish from the region will be safe to eat if, and only if, the mean naphthalene level in the region is less than 3.3 parts per billion. A set of water specimens will be randomly selected from the region and tested, and if the results provide convinving evidence that the mean naphthalene level is less than 3.3, then the sale of fish from the region will be made legal. Which of the following describes a Type I error and its consequences? A) the authorities fail to obtain convincing evidence that the mean naphthalene level is less than 3.3, and do not legalize the sale of fish from the region when in fact the fish are SAFE for consumption. B) The definition of a Type I error depends on the actual results of the study in question C) The authorities fail to obtain convincing evidence that the mean naphthalene level is less than 3.3, and do not…The mean number of sick days an employee takes per year is believed to be about 10. Members of a personnel department do not believe this figure. They randomly survey &8 employees. The number of sick days they took for the past year are as follows: 12; 6; 15; 3; 10; 8; 8; 8. Let X= the number of sick days they took for the past year. Should the personnel team believe that the mean number is about 10? Conduct a hypothesis test at the 5% level. What is the test statistic? (If using the z distribution round your answers to two decimal places, and if using the t distribution round your answers to three decimal places.) What is the p-value? (Round your answer to four decimal places.) Construct a 95% confidence interval for the true mean. Sketch the graph of the situation. Label the point estimate and the lower and upper bounds of the confidence interval. (Round your answers to three decimal places.)
- An important measure in the study of contagious infectious diseases is the number of cases directly generated by one previous case. Jessica is an epidemiologist studying the spread of an infectious disease in her country. She claimed that the mean number of cases directly generated by one previous case is now greater than 1.2. A study of 12 randomly selected cases of the disease is conducted and finds the sample mean number of cases directly generated by one previous case to be 1.5 with a sample standard deviation of 0.7. Assume that the population of the number of cases directly generated by one previous case is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 0.10 level of significance, to support the claim that u, the mean number of cases directly generated by one previous case, is greater than 1.2. (a) State the null hypothesis H, and the alternative hypothesis H, that you would use for the test.…Among 1815 randomly selected high school students surveyed by the Centers for Diseases Control, 300 said they were current smokers. b. Estimate the variability in such sample proportion by finding SE (p).12.A sample of n = 16 scores has a mean of M = 65 and an estimated standard error of 2 points. What is the sample variance? s2 = 64 c. s2 = 16 а. b. s2 = 36 d.s? = 4
- 3. Dentists make many people nervous. To assess any effect of such nervousness on blood pressure, the systolic blood pressure of 60 subjects was measured both in a dental setting and in a medical setting (The Effect of the Dental Setting on Blood Pressure Measurement," Amer. J. of Public Health, 1983:1210- 1214). For each subject, the difference between dental setting pressure and medical setting pressure was computed; the resulting sample mean difference and sample standard deviation of the differences were 4.47 and 8.77 mmHg, respectively. o (a) Estimate the true mean difference between blood pressures for these two settings using a 99% confidence level. o (b) Does it appear that the true mean pressure is different in a dental setting than in a medical setting? Explain your reasoning.The University of Montana admission standards require students to have an ACT score of at least 22.We know that Montana ACT scores are normally distributed with a mean of 20.1 and standarddeviation of 4. If we ask a random sample of 100 students who took the ACT, how many would be expected toqualify for admission to UM?7. In one state, the mean time served in prison by convicted burglars is 18.7 months. A researcher would like to perform a hypothesis test to determine whether the mean amount of time served by convicted burglars in her hometown is different from 18.7 months. She takes a random sample of 11 such cases from court files in her home town and finds that = 21.4 months and s = 7 months. Use a 5% significance level to perform the test. Assume normally distributed population. Perform critical-value (classical) test. Be sure to identify the null and alternate hypotheses and interpret your results. a) Hypotheses: b) Test statistic: c) Critical-value: d) Hypothesis test conclusion and interpretation:
- 8.What is the sample variance and the estimated standard error for a sample of n = 9 scores with SS = 72? a. s2= 9 and sM = 3 c. s²= 3 and sM = 3 b. s? = 9 and SM = 1 d. s2 = 3 and sM= 1 %3DGestation period is the length of pregnancy, or to be more precise, the interval between fertilization and birth. In Syrian hamsters, the average gestation period is 16 days. Suppose you have a sample of 31 Syrian hamsters who were exposed to high levels of the hormone progesterone when they were pups, and who have an average gestation length of 17.1 days and a sample variance of 26.0 days. You want to test the hypothesis that Syrian hamsters who were exposed to high levels of the hormone progesterone when they were pups have a different gestation length than all Syrian hamsters. Calculate the t statistic. To do this, you first need to calculate the estimated standard error. The estimated standard error is sMM= a. 31, b. 0.5232, c. 0.7328, d. 0.9158. The t statistic is- a. 1.50, b. 2.10, c. 2.63, d. 1.20 Now suppose you have a larger sample size n = 95. Calculate the estimated standard error and the t statistic for this sample with the same sample average and the same…A researcher predicts that smoking cigarettes decreases a person's sense of smell. On a test of olfactory sensitivity (smell), the mean for non-smokers is 18.4. A sample of 12 people who smoke a pack each day have a sample mean of 16.25 (sample variance = 4.75). Complete the following statement: We ["", ""] the null. Smokers have ["", "", ""] in olfactory sensitivity compared to non-smokers.