The lifespan of a 100-W fluorescent lamp is define to be normally distributed with o = 30 hrs. A random sample of 15 lamps has a mean life ofx = 1000 hours. Construct a 95% lower-confidence bound on the mean life.
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- A random sample of 81 ninth grade student's scores on a national mathematics assessment test has a mean score of 272. This test result prompts a state school administrator to declare that the mean score for the state's ninth graders on this exam is more than 270. Assume that the population standard deviation is 30. At alpha= 0.05, is there enough evidence to support the administrator's claim?The antibody production of 12 male red-winged blackbirds before and after receiving testosterone implants was compared. The units for antibody levels were natural log (10-3 optical density) per minute (In(mOD/min)). The mean change in antibody production was d = 0.056, and the standard deviation was sd = 0.225 If you were assigned the task of repeating this experiment, and wanted to ensure that you could detect a mean change of 0.02 units with a probability of 0.8, then what sample size would you use? Since we are calculating n for a study of individuals, answers should be rounded up to the next whole number.A shipping firm suspects that the mean life of a certain brand of tire used by its trucks is lessthan 38,500 miles. To check the claim, the firm randomly selects and tests 28 of these tires and gets a mean lifetime of 37,550 miles with a standard deviation of 1250 miles. At α = 0.02, test the shipping firm's claim. Round the test statistic to the nearest thousandth.
- The time it takes for a compact fluorescent bulb to reach full brightness is normally distributed with mean 29.9 seconds and standard deviation 4.1 seconds. Find and interpret the z-score for x = 26.4.The mean life span of an African savanna elephant in the wild used to be 60 years. A recent sample of 15 deceased elephants in the wild yielded a mean life span of 62 years. Assume a normally distributed population with = 6 years. Test if the population mean life span of African savanna elephants has increased, using a = 0.05. Select one: O a. p-value = 0.0984, do not reject Ho. O b. p-value = 0.0984, reject Ho. c. p-value = 0.1968, do not reject Ho. d. p-value = 0.4522, do not Reject Ho.Pyramid Lake is on the Palute Indian Reservation in Nevada. The lake is famous for cutthroat trout. Suppose a tells you that the average length of trout caught in Pyramid Lake Is mu = 19 Inches. Howevera survey reported that of a random sample of 46 fish caught, the mean length was overline x =18.6 lnch , with estimated standard s = 2.7 inches. these data Indicate that the average length of a trout caught in Pyramid Lake less than mu = 19 inches? Use a=0.05 Please answer ONLY parts D & E
- The lifetime of a particular component is normally distributed with a mean of 1000 hours and a standard deviation of 100 hours. What is the 80th percentile of component lifetimes?Currently patrons at the library speak at an average of 61 decibels. Will this average increase after the installation of a new computer plug in station? After the plug in station was built, the librarian randomly recorded 57 people speaking at the library. Their average decibel level was 63.8 and their standard deviation was 9. What can be concluded at the the αα = 0.10 level of significance?A trial study suggest that the standard deviation for the half life for the drug chlordiazepoxide is 8 hours. With 99% confidence, find the sample size needed to determine the mean half life for the drug with a margin of error of 3 hours.
- Calcium is essential to tree growth. In 1990, the concentration of calcium in precipitation in a certain area was 0.11milligrams per liter (mg/L).A random sample of 10 precipitation dates in 2018 results in the following data table. Complete parts (a) through (c) below. (B) With 98% confidence, the mean concentration of calcium in precipitation in this area in 2018 is betweenA company manufactures tennis balls. When its tennis balls are dropped onto a concrete surface from a height of 100 inches, the company wants the mean height the balls bounce upward to be 54.7 inches. This average is maintained by periodically testing random samples of 25 tennis balls. If the t-value falls between - to 99 and to 99, then the company will be satisfied that it is manufacturing acceptable tennis balls. A sample of 25 balls is randomly selected and tested. The mean bounce height of the sample is 56.7 inches and the standard deviation is 0.25 inch. Assume the bounce heights are approximately normally distributed. Is the company making acceptable tennis balls? Find -to 99 and to.99- - to.99 = to.99 = (Round to three decimal places as needed.) Find the t-value. t-value = Is the company making acceptable tennis balls? Choose the correct answer below. O A. The tennis balls are not acceptable because the t-value falls outside -tn og and to oa.A company manufactures tennis balls. When its tennis balls are dropped onto a concrete surface from a height of 100 inches, the company wants the mean height the bails bounce upward to be 55.4 inches. This average is maintained by periodically testing random samples of 25 tennis balls. If the t-value falls between - to 90 and to so. then the company will be satisfied that it is manufacturing acceptable tennis balls. A sample of 25 balls is randomly selected and tested. The mean bounce height of the sample is 56.2 inches and the standard deviation is 0.25 inch. Assume the bounce heights are approximately normally distributed. Is the company making acceptable tennis balls? Find - to so and to so -o s0 to so O (Round to three decimal places as needed.)