Exam 13: Inference for Counts: Chi-Square Tests

A manufacturer of cordless electric shavers sampled 13 from a day's production and found the mean time of continuous usage without recharging to be 410 minutes with a Sample standard deviation of 30 minutes. We can assume that times are normally Distributed. We wish to test if the true mean operating time without recharging is more Than 400 minutes. The correct calculated value of the test statistic is

A type II error is committed when

A local politician was interested in determining whether income level affects opinion regarding the government's bailout bill for easing the 2008 financial crisis on Wall Street. He surveyed a sample of his constituents and got the following results. The correct null Hypothesis to be tested is

A real estate agency, located in a metropolitan area in the northeastern U.S., kept data on the various types of properties purchased in the area. Historically, 15% of purchases Were for condominiums, 30% were for townhouses, 40% for single family homes, 10% For commercial properties and 5% for land. With changing demographics, the agency Wondered if the current distribution matches the historical distribution. Recent data Showed the following: Type of Property Condos Townhouses Homes Commercial Land Frequency 89 121 78 25 12 What is the standardized residual associated with Townhouses?

Previous surveys reported that more men than women trade stocks online. A local brokerage firm randomly selected a sample of investors. They found that 45 out of 234 Men traded online and 42 out of 251 women traded online. The 95% confidence interval For the difference in proportions is

An online department store wants to determine if there is an association between coupon redemption and gender. After a special coupon broadcast to its reward members, The following data on coupon redemption at check out were collected. The P-value Associated with the calculated Chi-square statistic is 0.0209. At α = 0.05 the correct Conclusion is Coupon Redeemed?

You should use a pooled t-test versus a non-pooled t-test when

An army depot that overhauls ground mobile radar systems is interested in improving its processes. One problem involves troubleshooting a particular component that has a High failure rate after it has been repaired and reinstalled in the system. The shop floor Supervisor believes that having standard work procedures in place will reduce the time Required for troubleshooting this component. Time (in minutes) required troubleshooting This component without and with the standard work procedure is recorded for a sample of 19 employees. In order to determine if having a standard work procedure in place Reduces troubleshooting time, they should use

The residual, or the difference, between the observed frequency and the expected frequency is a reliable indicator. A standardized residual can also be computed for each Cell. Which statements are true about standardized residuals?

An online department store wants to determine if there is an association between coupon redemption and gender. After a special coupon broadcast to its reward members, The following data on coupon redemption at check out were collected. Which Chi-square Test is most appropriate for this situation?

In economic downturns, companies attempt to downsize their workforces by offering early retirement incentives to older employees. A survey of 723 companies found that 195 engage in such downsizing practices. The 99% confidence interval for the Proportion of companies that downsize their workforces by offering early retirement Incentives is

Vending machines on a college campus offer a variety of snacks. The purchasing agent believes that each type of snack is equally preferred by students and consequently Orders equal quantities. The number of snacks sold from vending machines on this Campus for the last six months is shown in the following table. The correct value of the Test statistic for determining if the purchasing agent's belief if supported is Snack Type Chips Candy Bars Crackers Nuts Purchase Frequency 159 198 174 149

A real estate agency, located in a metropolitan area in the northeastern U.S., kept data on the various types of properties purchased in the area. Historically, 15% of purchases Were for condominiums, 30% were for townhouses, 40% for single family homes, 10% For commercial properties and 5% for land. With changing demographics, the agency Wondered if the current distribution matches the historical distribution. Recent data Showed the following: Type of Property Condos Townhouses Homes Commercial Land Frequency 89 121 78 25 12 Based on the historical distribution, we would expect how many homes to be purchased?

A real estate agency, located in a metropolitan area in the northeastern U.S., kept data on the various types of properties purchased in the area. Historically, 15% of purchases Were for condominiums, 30% were for townhouses, 40% for single family homes, 10% For commercial properties and 5% for land. Based on the data shown below, the null Hypothesis was rejected and the agency concluded that the current distribution of property Sales differs from the historical distribution. Based on an examination of the standardized Residuals, which type of property had the most impact on the test results? Type of Property Condos Townhouses Homes Commercial Land Frequency 89 121 78 25 12

Shape-Up-By-Susie claims that participating in her exercise program will result in guaranteed weight loss in just 6 weeks. Five clients weighed themselves before and then Again after participating in her program and the differences "weight after - weight Before" were analyzed. The relevant output is shown below. At the 0.05 level of Significance, the correct conclusion is Paired $T$ for After - Before Mean StDev SE Mean After 5 144.6 31.7 14.2 Before 5 148.0 28.9 12.9 Difference 5 -3.40 3.51 1.57 $95 \div$ upper bound for mean difference: $- 0.06$ T-Test of mean difference $= 0 ( \mathrm { vs } < 0 ) : \mathrm { T }$ -Value $= - 2.17$ P-Value $= 0.048$

A human resources manager at a large company wants to estimate the proportion of employees that would be interested in reimbursement for college courses. If she wishes To be 95% confident that her estimate is within 5% of the true proportion, how many Employees would need to be sampled?

A real estate agency, located in a metropolitan area in the northeastern U.S., kept data on the various types of properties purchased in the area. Historically, 15% of purchases were for condominiums, 30% were for townhouses, 40% for single family homes, 10% for commercial properties and 5% for land. With changing demographics, the agency wondered if the current distribution matches the historical distribution. Recent data showed the following: Type of Property Condos Townhouses Homes Commercial Land Frequency 89 121 78 25 12 A. State appropriate hypotheses to test whether the purchasing agent is correct. b. What is the value of the test statistic and its associated P-value? c. State the conclusion at α = .05.

A real estate agency, located in a metropolitan area in the northeastern U.S., kept data on the various types of properties purchased in the area. Historically, 15% of purchases Were for condominiums, 30% were for townhouses, 40% for single family homes, 10% For commercial properties and 5% for land. With changing demographics, the agency Wondered if the current distribution matches the historical distribution. Recent data Showed the following: Type of Property Condos Townhouses Homes Commercial Land Frequency 89 121 78 25 12 What is the standardized residual associated with Townhouses?

A manufacturing plant for recreational vehicles receives shipments from three different parts vendors. There has been a defect issue with some of the electrical wiring in the Recreational vehicles manufactured at the plant. The plant manager believes that the Defect issue is dependent on the parts vendor. The plant manager reviews a sample of Quality assurance inspections from the last six months. The correct value of the test Statistic for determining if the plant manager's belief is supported is

An online book store wants to determine if coupon redemption is independent of gender. After a special coupon broadcast to its reward members, the following data on coupon redemption at check out were collected. Coupon Redeemed? A. State appropriate hypotheses to determine whether coupon redemption is independent of gender. b. What is the value of the test statistic and its associated P-value? c. State the conclusion at α = .05.