ECN 221 Exam 2

A bank manager wishes to estimate the average waiting time for customers in line for tellers. A random sample of 50 times is measured and the average waiting time is 5.7 minutes. The sample standard deviation of waiting time is 2 minutes. Which Excel function would be used to find the margin of error to construct a confidence interval estimate? T.INV INT NORM.INV CONFIDENCE.T MARGIN.ERROR

CONFIDENCE.T

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 standard normal distribution can be used. The t distribution with 50 degrees of freedom must be used. The t distribution with 49 degrees of freedom must be used. The interval estimate will be invalid unless μ is known. The sample size must be increased in order to develop an interval estimate.

The t distribution with 49 degrees of freedom must be used.

The ability of an interval estimate to contain the value of the population parameter is described by the _____. sensitivity coefficient precise value of the population mean μ confidence level degrees of freedom None of the answers is correct.

confidence level

As the sample size increases, the variability among the sample means _____. decreases depends upon the specific population being sampled remains the same increases

decreases

When the population has a normal distribution, the sampling distribution of is normally distributed _____. for any sample from a finite population for any sample size for any sample size of 50 or more for any sample size of 30 or more

for any sample size

The standard deviation of a standard normal distribution _____. can be any positive value can be any value is always equal to 0 is always equal to 1

is always equal to 1

As a general rule, the sampling distribution of the sample proportions can be approximated by a normal probability distribution whenever _____. np ≥ 5 np≥ 5 or n(1 −p) ≥ 5 n ≥ 30 np ≥ 5 and n(1 − p) ≥ 5 n(1 − p) ≥ 5

np ≥ 5 and n(1 − p) ≥ 5

A single numerical value used as an estimate of a population parameter is known as a_____. population parameter parameter parameter or a population parameter point estimate

point estimate

In point estimation, data from the _____. None of the answers is correct. sample are used to estimate the sample statistic population are used to estimate the population parameter sample are used to estimate the population parameter

sample are used to estimate the population parameter

The margin of error in an interval estimate of the population mean is a function of all of the following EXCEPT _____. variability of the population sample mean sample size level of significance

sample mean

The degrees of freedom associated with a t distribution are a function of the _____. sample size area in the upper tail sample standard deviation confidence coefficient

sample size

The standard deviation of all possible values is called the _____. mean deviation central variation standard error of proportion standard error of the mean

standard error of the mean

To compute the minimum sample size for an interval estimate of μ when the population standard deviation is known, we must first determine all of the following EXCEPT _____. the degrees of freedom the known population standard deviation the confidence level the desired margin of error

the degrees of freedom

The t distribution should be used whenever _____. the population is not normally distributed the true population mean is unknown None of the answers is correct. the sample size is less than 30 the sample standard deviation is used to estimate the population standard deviation

the sample standard deviation is used to estimate the population standard deviation