Exam 8: Interval Estimation

In order to estimate the average electric usage per month, a sample of 64 houses was selected and the electric usage was determined. Assume a population standard deviation of 320 kilowatt-hours. The standard error of the mean is

We are interested in conducting a study in order to determine the percentage of voters in a city who would vote for the incumbent mayor. What is the minimum sample size needed to estimate the population proportion with a margin of error not exceeding 4% at 95% confidence?

An estimate of a population parameter that provides an interval of values believed to contain the value of the parameter is known as the

If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect the

Using an α = .04, a confidence interval for a population proportion is determined to be .65 to .75. For the same data, if α is decreased, the confidence interval for the population proportion

A sample of 100 information systems managers had an average hourly income of $40.00 with a standard deviation of $8.00. The standard error of the mean is

In order to estimate the average time spent per student on the computer terminals at a local university, data were collected for a sample of 64 business students over a one-week period. Assume the population standard deviation is 1.6 hours. With a .95 probability, the margin of error is approximately

In 2015, approximately 136,943,000 people visited an emergency room in the United States. Of these, approximately 12,263,000 were subsequently admitted to the hospital. Provide a 99% confidence interval for the proportion of people visiting an emergency room who were subsequently admitted to the hospital.

A machine that produces a major part for an airplane engine is monitored closely. In the past, 6% of the parts produced would be defective. With a .95 probability, the sample size that needs to be taken if the desired margin of error is .04 or less is

The t value for a 95% confidence interval estimation with 96 degrees of freedom is

A random sample of 1000 people was taken. Seven hundred fifty of the people in the sample favored Candidate A. The 95% confidence interval for the true proportion of people who favor Candidate A is

To compute the minimum sample size for an interval estimate of μ, we must first determine all of the following except

A random sample of 100,000 credit sales in a department store showed an average sale of $87.25. From past data, it is known that the standard deviation of the population is $20.00. What is the 95% confidence interval of the population mean?

In a sample of 400 voters, 360 indicated they favor the incumbent governor. The 95% confidence interval of voters not favoring the incumbent is

A random sample of 64 SAT scores of students applying for merit scholarships showed an average of 1400 with a standard deviation of 240. The 95% confidence interval for the population mean SAT score is

The probability that the interval estimation procedure will generate an interval that does not contain the actual value of the population parameter being estimated is the​

For the interval estimation of μ when σ is known and the sample is large, the proper distribution to use is the

A sample of 100 information systems managers had an average hourly income of $40.00 with a standard deviation of $8.00. If we want to determine a 95% confidence interval for the average hourly income of the population, the value of t is

The manager of a grocery store has taken a random sample of 144 customers. The average length of time it took these 144 customers to check out was 3 minutes. It is known that the standard deviation of the population of checkout times is 1 minute. The standard error of the mean equals

A random sample of 25,000 ACT test takers had an average score of 21 with a standard deviation of 5. Determine the standard error.