Exam 8: Statistical Inference: Estimation for Single Populations

Suppose a random sample of size 64 is selected from a population yielding a sample mean of 26.The population standard deviation is 4.From this information,the 90% confidence interval to estimate the population mean can be computed to be ___.

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 ___.

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

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.

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 ___.

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

The normal distribution is used to test about a population mean for large samples if the population standard deviation is known."Large" is usually defined as ___.

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 ___.

Like a t distribution,a chi-square distribution is symmetrical and extends from minus infinity to plus infinity.

A random sample of 225 items from a population results in 60% possessing a given characteristic.Using this information,the researcher constructs a 90% confidence interval to estimate the population proportion.The resulting confidence interval is ___.

A random sample of 64 items is selected from a population of 400 items.The sample mean is 200.The population standard deviation is 48.From this data,a 90% confidence interval to estimate the population mean can be computed as ___.

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

A researcher wants to estimate the proportion of a population which possesses a given characteristic.A random sample of size 200 is taken and 30% of the sample possesses the characteristic.The 95% confidence interval to estimate the population proportion is ___.

When a range of values is used to estimate a population parameter,it is called a range estimate.

The z value associated with a two-sided 95% confidence interval is ___.

A study is going to be conducted in which a population mean will be estimated using a 92% confidence interval.The estimate needs to be within 12 of the actual population mean.The population variance is estimated to be around 2500.The necessary sample size should be at least ___.

A researcher is interested in estimating the mean value for a population.She takes a random sample of 17 items and computes a sample mean of 224 and a sample standard deviation of 32.She decides to construct a 98% confidence interval to estimate the mean.The degrees of freedom associated with this problem are ___.

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 ___.

A researcher wants to estimate the population proportion with a 95% level of confidence.He estimates from previous studies that the population proportion is no more than .30.The researcher wants the estimate to have an error of no more than .03.The necessary sample size is at least ___.

A random sample of 64 items is selected from a population of 400 items.The sample mean is 200.The population standard deviation is 48.From this data,a 95% confidence interval to estimate the population mean can be computed as ___.