Exam 8: Interval Estimation

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. Determine the standard error of the mean.

In November 2018, 50,000 people living in the United States were asked whether they had a computer at home. 43,128 answered yes, they had a computer at home. Provide a 99% confidence interval for the proportion of people living in the United States who have a computer at home.

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. With a .95 probability, the sample mean will provide a margin of error of

To compute the necessary sample size for an interval estimate of a population mean, all of the following procedures are recommended when σ is unknown except​

The mean of the t distribution is​

A sample of 225 elements from a population with a standard deviation of 75 is selected. The sample mean is 180. The 98% confidence interval for μ is

The sample size needed to provide a margin of error of 3 or less with a .95 probability when the population standard deviation equals 11 is

In order to determine an interval for the mean of a population with unknown standard deviation, a sample of 58 items is selected. The mean of the sample is determined to be 36. The associated number of degrees of freedom for reading the t value is

The following random sample from a population whose values were normally distributed was collected. 10 12 18 16 ​ The 80% confidence interval for μ is

When constructing a confidence interval for the population mean using the standard deviation of the sample, the degrees of freedom for the t distribution equals

A sample of 100 information systems managers had an average hourly income of $40.00 with a standard deviation of $8.00. The value of the margin of error at 95% confidence 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. If we want to provide a 95% confidence interval for the population mean SAT score, the degrees of freedom for reading the t value is

In an interval estimation for a proportion of a population, the value of z at 99.2% confidence is

It is known that the population variance equals 529. With a .95 probability, the sample size that needs to be taken if the desired margin of error is 4 or less is

The ability of an interval estimate to contain the value of the population parameter is described by the

From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for µ. Which of the following statements is true?​

The level of significance α

From a population that is normally distributed, a sample of 25 elements is selected and the standard deviation of the sample is computed. For the interval estimation of μ, the proper distribution to use is the

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. With a .95 probability, determine the margin of error.

The sample size that guarantees the estimate of a population proportion satisfying the margin of error requirement is computed using a planning value of p equal to​