Exam 13: Inference for Counts: Chi-Square Tests

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. Find the 95% confidence interval for the difference in proportions. Interpret.

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. A. State appropriate hypotheses to test the plant manager's belief. b. What is the value of the test statistic and its associated P-value? c. State the conclusion at α = .05.

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 null hypothesis to test his belief can be worded as

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 performed a Chi-square test. The resulting P-value was 0.024. At the 0.01 level of significance, he should conclude that

Which of the following is not an assumption or condition that needs to be checked for a paired t-interval?

After computing a confidence interval, the investigator believes that the results are meaningless because the width of the interval is too large. In reconstructing the interval, The investigator should

A truck company wants on-time delivery for 98% of the parts they order from a metal manufacturing plant. They have been ordering from Hudson Manufacturing but will Switch to a new, cheaper manufacturer (Steel-R-Us) unless there is evidence that this New manufacturer cannot meet the 98% on-time goal. As a test the truck company Purchases a random sample of metal parts from Steel-R-Us, and then determines if These parts were delivered on-time. Which hypotheses should they test?

Before being released to market, a drug company tests a new allergy medication for potential side effects. A random sample of 160 individuals with allergies was selected for the study. The new allergy medication was randomly assigned to 80 of them, and another popular allergy medication already on the market (Brand C) was assigned to the rest. Out of the 80 given the new allergy medication, 14 reported drowsiness; 22 of the 80 taking Brand C reported drowsiness. Compute the 95% confidence interval for the difference in proportions reporting drowsiness. Interpret.