The mean life of a sample of 10 electric light bulbs wasfound to be 1.456 hours with standard deviation of 423hours. A second sample of 17 bulbs chosen from adifferent batch showed a mean life of 1,280 hours withstandard deviation of 398 hours. Is there a significantdifference between the means of the two samples ?

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Answered: The mean life of a sample of 10…

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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Lake Quanipaug in Connecticut is famous for its yellow perch. Studies have found that the national mean length is µ = 8.2 inches. However, a random sample of 31 fish caught during Memorial weekend at Lake Quanipaug, had a sample mean of x̄=7.1 inches, with an estimated sample standard deviation of s = 3.8 inches. Do these current data indicate that the average length of the yellow caught at Lake Quanipaug is less than historical µ = 8.2 inches? Use α = .02. State α, Ho, H1, p-value, rejection, or non-rejection, and be certain to interpret your results.
The mean BMI in patients free of diabetes has been reported as 27.8. An investigator measured BMI in 12 patients who are free of diabetes and found a mean BMI of 30.2 with a standard deviation of 5.5. The investigator hypothesizes that the BMI in patients free of diabetes is higher than what has been reported. Is there evidence that the BMI is significantly higher that 27.8? Use a 5% level of significance. Give each of the following to receive full credit: 1) the appropriate null and alternative hypotheses; 2) the appropriate test; 3) the decision rule; 4) the calculation of the test statistic; and 5) your conclusion including a comparison to alpha or the critical value. You MUSTshow your work to receive full credit. Partial credit is available.
The lifetimes of a certain brand of battery are assumed to be normally distributed with a mean of 405 hours. Find the standard deviation of these battery lifetimes, if 90% of these batteries do not achieve a lifetime of 411 hours.
In a study by WebCriteria, it took an average of 2.1 minutes to locate information and buy products on the Delta Airlines website, compared to an average of 2.7 minutes on the British Airways site. Assuming normal populations with equal standard deviations, data from sheet 3 contains the times (in minutes) required during visits to the two websites. In a suitable one-tail test at the 0.01 level, was the mean time for the Delta visits significantly less than that for the British Airway visits? Sheet 3 Delta British 2,12 2,44 1,40 2,51 2,03 2,48 2,00 2,88 2,34 2,60 1,63 2,38 1,96 2,77 3,36 2,96 1,69 2,82 2,01 2,45 1,86 3,29 2,08 3,05 2,61 2,03 1,62 3,18 1,67 2,65 2,17 2,94 2,69 3,31 2,34 2,93 2,25…
A number of 28 university students who smokes completed a questionnaire inquiring their smoking history and behavior. The result shows that the average smoking initiation age of this group is 21.6 years with a variance of 18.49. Based on past record, the smoking initiation age of university student has a mean of 20.74 years with a standard deviation of 5.1 years. Conduct a necessary analysis to determine if the smoking initiation age remain the same as the previous record. Use 4% level of significance.
Assume the average amount of caffeine consumed daily by adults is normally distributed with a mean of 260 mg and a standard deviation of 48 mg. In a random sample of 600 adults, how many consume at least 320 mg of caffeine daily?
Suppose the total weight of passengers on a particular flight has a mean of 1499 with standard deviation 128 what is the score of a flight with a total weight of 1639.8
A tire manufacturer claims that the mean life of its tire is 75,000 miles. The mean of a sample of 50 tires is 74,200 miles with a standard deviation of 2300 miles. Using an alpha of 5%, does the manufacturer’s claim appear to hold ture? Explain.
A manufacturer of TV tubes has for many years used a process giving a meantube life of 4700 hours and a standard deviation of 1460 hours. A new process is tried to see if it will increase the life significantly. A sample of 100new tubes gave a mean life of 5000 hours. Is the new process better than the old one at a 1% level of significance?
A half-century ago, the mean height of women in a particular country in their 20s was 62.3inches. Assume that the heights of today's women in their 20s are approximately normally distributed with a standard deviation of 2.25inches. If the mean height today is the same as that of a half-century ago, what percentage of all samples of 29of today's women in their 20s have mean heights of at least 63.41 inches?
What raw score for age corresponds to a z- score of +4.50, given a mean of 12.0 years and a standard deviation of 4.0 years?
A research firm supplies manufacturers with estimates of the sales of their products from samples of stores. Marketing managers often look at the sales estimates and ignore sampling error. An SRS of 50 stores this month shows mean sales of 41 units of a particular appliance with standard deviation of 11 units. During the same month last year, an SRS of 52 stores gave mean sales of 38 units of the same appliance with a standard deviation of 13units. An increase from 38to 41 is a rise of 7.9%.. The marketing manager is happy because sales are up 7.9%. (a) Give a 95%confidence interval for the difference in mean number of units of the appliance sold at all retail stores. Give your answers to three decimal places. lower bound: upper bound:

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