Exam 8: Statistical Inference: Estimation for Single Populations

In estimating the sample size necessary to estimate a population mean, the error of estimation, E, is equal to the difference between the sample mean and the population mean.

The table t value associated with the upper 5% of the t distribution and 12 degrees of freedom is ___.

Suppose a random sample of 36 is selected from a population with a standard deviation of 12.If the sample mean is 98, the 99% confidence interval to estimate the population mean is ___.

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications.A random sample of 200 email messages was selected.Thirty of the messages were not business related.The 95% confidence interval for the population proportion is ___.

The table t value associated with the upper 10% of the t distribution and 23 degrees of freedom is ___.

Suppose a random sample of 36 is selected from a population with a standard deviation of 12.If the sample mean is 98, the 90% confidence interval for the population mean is ___.

Elwin Osbourne, CIO at GFS, Inc., is studying employee use of GFS email for non-business communications.A random sample of 200 email messages was selected.Thirty of the messages were not business related.The point estimate for this population proportion is ___.

Catherine Chao, Director of Marketing Research, is evaluating consumer acceptance of a new toothpaste package.She randomly selects a sample of 200 households.Forty households prefer the new package to all other package designs.The 90% confidence interval for the population proportion is ___.

The table t value associated with the upper 5% of the t distribution and 14 degrees of freedom is ___.

The lengths of steel rods produced by a shearing process are normally distributed.A random sample of 10 rods is selected; the sample mean length is 119.05 centimetres; and the sample standard deviation is 0.10 centimetres.The 90% confidence interval for the population mean rod length is ___.

Catherine Chao, Director of Marketing Research, is evaluating consumer acceptance of a new toothpaste package.Her staff reports that 17% of a random sample of 200 households prefers the new package to all other package designs.If Catherine concludes that 17% of all households prefer the new package, she is using a ___.

A researcher wants to estimate the proportion of a population which possesses a given characteristic.A random sample of size 250 is taken and 40% of the sample possesses the characteristic.The 90% confidence interval to estimate the population proportion is ___.

If the degrees of freedom in a t distribution increase, difference between the t values and the z values will also increase.

In determining the interval estimates for a population proportion using the sample proportion, it is appropriate to use the values from a t distribution rather than the z distribution.

James Desreumaux, VP of Human Resources of Maritime Boat Manufacturing (MBM), is reviewing the employee training programs of MBM factories.His staff randomly selected personnel files for 10 workers in Nova Scotia, and determined that their mean training time was 25 hours and that the standard deviation was 5 hours.Assume that training times are normally distributed.The 90% confidence interval for the population variance of training times is ___.

In determining the interval estimates for a population variance using the sample variance, it is appropriate to use the values from a chi-square distribution rather than a t distribution.

Given n = 20, s = 32, and that the population is normally distributed, the 90% confidence interval for the population variance is ___.

Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers.Accordingly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes.Assume that the population standard deviation is 4 minutes.The 90% confidence interval for the population mean of waiting times is ___.

The z value associated with a two-sided 90% confidence interval is ___.

Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers.Accordingly, his staff recorded the waiting times for 45 randomly selected walk-in customers, and calculated that their mean waiting time was 15 minutes.If Brian concludes that the average waiting time for all walk-in customers is 15 minutes, he is using a ___.