Question 3. Customers sometimes have to wait a long time to speak to acustomer service representative when they call regarding disputed chargeswith a cell phone provider. A random sample of 25 such calls yielded amean waiting time of 22 minutes with a standard deviation of 6 minutes.Construct a 99% confidence interval for the population mean of suchwaiting times. Assume that such waiting times for the population follow anormal distribution.

From the provided information, Sample size (n) = 25 Sample mean (x̄) = 22 Sample standard deviation…

Answered: Question 3. Customers sometimes have to…

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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Suppose the finishing times for cyclists in a race are normally distributed. If the population standard deviation is 16 minutes, what minimum sample size is needed to be 90% confident that the sample mean is within 5 minutes of the true population mean?
Students preparing for comprehensive exams usually spend many hours studying. Suppose it is known that the time students spend studying for comprehensive exams has a distribution that is skewed heavily to the right with a mean of 41.3 hours and a standard deviation of 6.8 hours. If a simple random sample of 72 students is selected and the amount of time each spent studying for the comprehensive exam is determined. State and check the two assumptions.
Fran is training for her first marathon, and she wants to know if there is a significant difference between the mean number of miles run each week by group runners and individual runners who are training for marathons. She interviews 42 randomly selected people who train in groups and finds that they run a mean of 47.1 miles per week. Assume that the population standard deviation for group runners is known to be 4.4 miles per week. She also interviews a random sample of 47 people who train on their own and finds that they run a mean of 48.5 miles per week. Assume that the population standard deviation for people who run by themselves is 1.8 miles per week. Test the claim at the 0.01 level of significance. Let group runners training for marathons be Population 1 and let individual runners training for marathons be Population 2. Step 2 of 3 : Compute the value of the test statistic. Round your answer to two decimal places.
Many people consider their smart phone to be essential! Communication, news, Internet, entertainment, photos, and just keeping current are all conveniently possible with a smart phone. However, the battery better be charged or the phone is useless. Battery life of course depends on the frequency, duration, and type of use. One study involving heavy use of the phones showed the mean of the battery life to be 11.25 hours with a standard deviation of 3.3 hours. Then the battery needs to be recharged. Assume the battery life between charges is normally distributed. (a) Find the probability that with heavy use, the battery life exceeds 12 hours. (Round your answer to four decimal places.)(b) You are planning your recharging schedule so that the probability your phone will die is no more than 5%. After how many hours should you plan to recharge your phone? (Round your answer to the nearest tenth of an hour.) hours
4. A fire extinguisher salesman would like to estimate the mean number of home fires started by candles each year. He obtained fire data for seven randomly selected years from the National Fire Protection Agency. His sample produced a mean of 7041 fires with a standard deviation of 1600. Create the 90% confidence interval of interest.
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 is
Suppose you have a sample of size 100 with mean 5 and standard deviation 2. Construct a 95% confidence interval for the population mean.
A researcher for the National Highway Traffic Safety Administration wishes to estimate the average bloodalcohol concentration (BAC) for drivers involved in fatal accidents who are found to have positive BAC values.He randomly selects records from 1,200 such drivers and determines the sample mean BAC to be 0.16g/dL.and standard deviation 0.08 g/dL. Construct a 96% confidence interval for the mean BAC.
In one city, the average amount of time that tenth-graders spend watching television each week is 23 hours. The principal of Birchwood High School believes it is less for the 10th grade students that at his school. For a sample of 95 tenth-graders from the school, the mean amount of time spent watching television per week was 21.9 hours. Assuming a population standard deviation of 3.1 hours, does the data provide sufficient evidence to conclude that for all tenth-graders at Birchwood High school, the mean amount of time spent watching television per week is less than the city average of 23 hours? Perform the appropriate hypothesis test using a significance level of 0.005. What are the hypotheses? What is the test statistic? Is it a z or a t? Find the P-value for this test statistic. How does it compare to the significance level? On the normal curve, indicate the location of the test statistic and the p-value. (label them on the graph) Write…
A researcher is conducting a study to determine the mean trough dosage of medication for a population. Assume a previous study was conducted for the same medication and the mean trough dose was found to be 490 mg with a standard deviation of 30 mg. If the researcher wants to be 95% confident the true mean trough dosage of the medication is within 10 mg of the true mean trough dosage, what sample size is needed if the study is predicted to have an 76% retention rate? n = 50 n = 71 n = 47 n = 104

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