manufacturer of Energy Saving Lamps has a product life that is normally distributed with a standard deviation of 45 hours. If a sample of 32 lamps having an average life of 775 hours, find the 96% confidence interval for the population mean of all the lamps produced by this manufacturer
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A manufacturer of Energy Saving Lamps has a product life that is
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- The ages of registered voters in Smith County are normally distributed with a population standard deviation of 3 years and an unknown population mean. A random sample of 18 voters is taken and results in a sample mean of 55 years. Find the margin of error for a 95% confidence interval for the population mean. z0.10z0.10 z0.05z0.05 z0.025z0.025 z0.01z0.01 z0.005z0.005 1.282 1.645 1.960 2.326 2.576 You may use a calculator or the common z values above. Round the final answer to two decimal places.You have obtained the number of years of education from one random sample of 38 police officers from City A and the number of years of education from a second random sample of 30 police officers from City B. The average years of education for the sample from City A is 15 years with a standard deviation of 2 years. The average years of education for the sample from City B is 14 years with a standard deviation of 2.5 years. Is there a statistically significant difference between the education levels of police officers in City A and City B?What is the appropriate test for this case? 2 sample z-testChi-square test 2-sample t-test2 sample paired t-test Carry out the test. The test statistic = (round answer to two decimal places.)and the p-value is (round answer to 2 decimal places)There sufficient evidence at the 5% level to conclude that the education levels of police officers in City A and City B is significantly different.The length of a doohickey is normally distributed with a standard deviation of 8 inches. If a random sample of 16 doohickeys has an average length of 30 inches find a 96% confidence interval for the mean of the lengths of the doohickeys.
- A random of 15 freshmen takers obtained a mean score of 74 and a variance of 9 on a SASE. Assuming the scores to be normally distributed, construct a 95% confidence interval to estimate the variance of scores of the whole freshmen population.Bone mineral density (BMD) is a measure of bone strength. Studies show that BMD declines after age 45. The impact of exercise may increase BMD. A random sample of 59 women between the ages of 41 and 45 with no major health problems were studied. The women were classified into one of two groups based upon their level of exercise activity: walking women and sedentary women. The 39 women who walked regularly had a mean BMD of 5.96 with a standard deviation of 1.22. The 20 women who are sedentary had a mean BMD of 4.41 with a standard deviation of 1.02. Which of the following inference procedures could be used to estimate the difference in the mean BMD for these two types of womenThe breaking strengths of cables produced by a certain manufacturer have historically had a mean of 1800 pounds and a standard deviation of 90 pounds. The company believes that, due to an improvement in the manufacturing process, the mean breaking strength, μ, of the cables is now greater than 1800 pounds. To see if this is the case, 100 newly manufactured cables are randomly chosen and tested, and their mean breaking strength is found to be 1818 pounds. Can we support, at the 0.05 level of significance, the claim that the population mean breaking strength of the newly- manufactured cables is greater than 1800 pounds? Assume that the population standard deviation has not changed. Perform a one-tailed test. Then complete the parts below. Carry your intermediate computations to three or more decimal places, and round your responses as specified below. (If necessary, consult a list of formulas.) (a) State the null hypothesis Ho and the alternative hypothesis H₁. H :O 1 (b) Determine the…
- An agricultural researcher plants 14 plots with a new variety of corn. The average yield for these plots is X = 155 bushels per acre. Assume that the yield per acre for new variety of corn follows a normal distribution with unknown mean and a calculated sample standard deviation s = 10 bushels. A 90% confidence interval for the unknown mean isA sample of 100 postal employees found that the mean time these employees had worked for the postal service was eight years. Assume we know the standard deviation of the population of times postal service employees have spent with the postal service is five years. Find the 98% confidence interval for the mean time the population of postal service employees have spent with the postal service.Suppose a random sample of 50 baksetball players showed the average height to be 78 inches. Also assume that the population standard deviation is 1.5 inches. Find 99% confidence interval for the population mean height.
- A ecologist wishes to estimate the mean lifespan for a specific species of bird. Assume that bird lifespan is normally distributed and that each bird's lifespan is independent of all others. The researcher analyzes a random sample of n=7 deceased birds to find out how long they lived for. It is found that the mean lifespan in the sample is y= 5 4 years with standard deviation s=13 years. Choose the correct formula for a 95% confidence interval for the true mean lifespan. X± to.975,n O xt to.975,n-1 n-1 O none of these X+ Z0.975 O x+ to.975,n-1' O xt to.975,n-15The IQ’s of 120 applicants for an apprenticeship are approximately normally distributed with a mean of 110 and a standard deviation of 11. If the apprenticeship program requires at least an IQ of 100, how many of these students will be rejected regardless of other qualifications?A sample of 6 credit ratings for car loan applicants has a mean of 602 and a variance of 4356. Use the data toconstruct a 90% confidence interval for the population standard deviation of credit scores for all applicantsfor car loans. What is the Best point estimate and Include the written statement
