Exam 11: Statistical Inference Concerning Variance

The following table shows the annual returns (in percent)for the Fidelity Utilities fund from 2006 through 2010. a.Calculate the point estimate of σ². b.Construct a 95% confidence interval of σ².

Suppose Apple would like to test the hypothesis that the standard deviation for the web-browsing battery life of the iPad equals 3.0 hours.The following data represents the battery life,in hours,experienced by a random sample of six users: 10 14 12 16 10 6. Which of the following would be the correct hypothesis test?

The population variance is one of the most widely used quantitative measures of risk in investments.

Construct a 95% interval estimate of the ratio of the population variances using the following results from two independently drawn samples from normally distributed populations.

The result of placing a larger sample variance in the numerator of the test statistic allows us to

The following are the competing hypotheses and the relevant summary statistics: . Which of the following is the critical value at the 5% significance level?

Which of the following Excel functions is used to calculate the exact probability for a left-tailed is distribution?

Which of the following hypotheses depicts a right-tailed test for the population variance?

Amie Jackson,a manager at Sigma travel services,makes every effort to ensure that customers attempting to make online reservations do not have to wait too long to complete the reservation process.The travel website is open for reservations 24 hours a day,and Amie regularly checks the website for the waiting time to maintain consistency in service.She uses the following independently drawn samples of wait time during two peak hours,morning 8a.m.to 10 a.m.and evening 7p.m.to 9p.m. ,for the analysis.Assume that wait times are normally distributed. Which of the following is the correct value of the test statistic?

The values of the distribution range from negative infinity to infinity.

The following are the competing hypotheses and the relevant summary statistics: The p-value associated with the value of the test statistic is 0.3692.At the 5% significance level,which of the following conclusions is correct?

It is preferable to place the smaller sample variance in the numerator of the statistic.

The relevant value on the ____ tail of the distribution is .

The _____ is the probability distribution of the sum of several independent squared standard normal random variables.

A random sample of 10 homes sold during last month in the city of Fontana had the following number of bedrooms in each house: 4,2,3,5,4,3,3,4,5,3. At α = 0.01,test the claim that the variance of a normally distributed population is less than 1 using a.the p-value approach. b.the critical value approach.

A financial analyst maintains that the risk,measured by the variance,of investing in emerging markets is more than 280(%)².Data on 20 stocks from emerging markets revealed the following sample results: = 12.1% and s² = 361(%)².Assume that the returns are normally distributed.Which of the following is the correct conclusion of the financial analyst's claim?

Annual growth rates for individual firms in the toy industry tend to fluctuate dramatically,depending on consumers' tastes and current fads.Consider the following growth rates (in percent)for two companies in this industry,Hasbro and Mattel. Which of the following is(are)the critical value(s)at α = 0.05?

We conduct the following hypothesis test .For a random sample of 15 observations,the sample standard deviation is 12.Which of the following is the correct approximation of the p-value used to conduct this test?

The manager of a video library would like the variance of the waiting times of the customers not to exceed 2.30 minutes-squared.He would like to add an additional billing counter if the variance exceeds the cut-off.He checks the recent sample data.For a random sample of 24 customer waiting times,he arrives at a sample variance of 3.8 minutes-squared.The manager assumes the waiting times to be normally distributed.Which of the following would be null and the alternate hypothesis to test if the cut-off is surpassed?

Which of the following characteristics is true regarding the F distribution?