Exam 7: Data for Decisions

The type of statistical study that can show cause and effect is:

A national poll asked 1581 adults whether they were satisfied with their jobs, and 54% said they were. Estimate a 95% confidence interval for the actual percentage among all adults.

A prospective study may be used to show cause and effect.

Use the following to solve the questions A poll of 827 students at Alpha State College found that 61% of those polled preferred a quarter system to a trimester system. -If the student population at Alpha State is 8000, what is a good estimate for the number who prefer a trimester system?

We must use a random digits table to choose a sample of eight names from the roster of a club with 100 members. Why can we use two-digit numbers from the table to select our sample?

Officials at a university conduct a survey to determine the percentage of students who favor the allocation of a percentage of tuition funds toward the construction of a new campus parking garage. One thousand people driving through the administration building parking lot are surveyed, and it is found that 75% of these people favor the garage. Explain why this conclusion might not be valid.

In order to determine what proportion of a town's residents approves of a new plan for trash collection, the town council placed an ad in the newspaper asking residents to phone in their opinions. Explain why the results of this poll may differ from the actual beliefs of all residents in the town.

Random selection of subjects in a survey is used to eliminate variability in results.

The marketing department of a large national corporation wishes to determine what proportion of the residents of a state may be interested in buying its new product. Describe how the corporation might use a multistage random sampling process to choose a sample of the state's residents to survey.

A random sample of 600 voters in Centralville indicated that 48 of them believed their congressional representative was honest and trustworthy. The sample proportion is:

Why do opinion polls usually report a margin of error with the results of a survey? What does the margin of error mean?

If the design of a statistical study favors systematically certain outcomes, the design has:

For an exit poll of an election, Candidate A obtained 53.6% of the total sample votes. If the 95% confidence interval is 51.8% to 55.4%, then we may infer that Candidate A is the winner of the election with 95% confidence.

Use the following to solve the questions A poll of 827 students at Alpha State College found that 61% of those polled preferred a quarter system to a trimester system. -Estimate a 95% confidence interval for the percentage of students who prefer a quarter system.

A group of 200 students is identified. Half took Latin in high school and half did not. The students are compared to see if the students who took Latin received higher SAT verbal scores. This type of study is a(n):

In order to determine the proportion of voters in a small town who favor a candidate for mayor, the campaign staff takes out an ad in the paper asking voters to call in their preference for mayor. This type of sample is a:

A survey of 127 patients in a particular hospital determined that 54% of them felt that they were receiving excellent care. Determine the 95% confidence interval for this survey.

A high school principal wishes to determine what proportion of the school's students likes the new school mascot. The principal decides to survey every 25th name from the school enrollment records (an alphabetical list of all students at the school). Is this a valid simple random sampling technique? Why or why not?

Convenience samples are said to be highly likely to produce bias in survey results. Explain why this is true.