The lifespan of a 100-W fluorescent lamp is define to be normally distributed with σ = 30 hrs. A random sample of 15 lamps has a mean life of x = 1000 hours. Construct a 90% lower-confidence bound on the mean life.
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The lifespan of a 100-W fluorescent lamp is define to be
Construct a 90% lower-confidence bound on the mean life.
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- A survey taken several years ago found that the average time a person spent reading the local daily newspaper was 10.8 minutes. The standard deviation of the population was 3 minutes. To see whether the average time had changed since the newspaper's format was revised, the newspaper editor surveyed 37 individuals. The average time that the 37 people spent reading the paper was 12.3 minutes. At =α0.01 , is there a change in the average time an individual spends reading the newspaper? Find the 99% confidence interval of the mean. Find the 99% confidence interval of the mean. Round the answers to nearest whole number. <<μThe 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.Does it take less time for seeds to germinate if they are near rock music that is continuously playing compared to being near classical music? The 41 seeds that were exposed to rock music took an average of 20 days to germinate. The standard deviation was 13 days. The 53 seeds that were exposed to classical music took an average of 23 days to germinate. The standard deviation for these seeds was 7 days. What can be concluded at the αα = 0.05 level of significance? The test statistic t = (please show your answer to 3 decimal places.) The p-value = (Please show your answer to 4 decimal places.)
- 100 specimens are tested in determining the life cycle of a certain type of crank shaft which is used in a particular brand of car engine. The tests have shown an average life cycle of μ=44 Gc (1 Gc = 1 gigacycles = 109 cycles) and a standard deviation of σ=33x10-1 Gc. 200 hundred thousand cars using that engine have been sold and are on the traffic. After what number of Gigacycles would you expect 7 % of the shafts broken down?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?For the following PDF and CDF graphics of a uniform distribution, if n=5 and t=5, find (c-v) = ? t W- m n d (x), F(X) - CDF function
- 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 sample is selected from a population with = 150. After a treatment is administered to the individuals, the sample mean is found to be = 140 and the standard deviation is S= 9. If the sample has n = 18 scores, determine whether the sample is sufficient to conclude that the treatment has significant effect. Use a two tail test with = 0.02.
- 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.)A psychologist is studying smokers' self-images, which she measures by the self-image (SI) score from a personality inventory. For adults in the U.S., the mean SI score from this inventory is about 150. The psychologist gathers a random sample of 16 SI scores of smokers and finds that their mean is 130 and their standard deviation is 31. Assume that the population of SI scores of smokers is normally distributed with mean μ. Based on the sample, can the psychologist conclude that μ is different from 150? Use the 0.05 level of significance. Perform a two-tailed test. Then fill in the table attached. Carry your intermediate computations to at least three decimal places and round your answers as specified in the table.