STATS

Computing the necessary sample size for an interval estimate of a population proportion requires a planning value for . In case of any uncertainty about an appropriate planning value, we know the value that will provide the largest sample size for a given level of confidence and a given margin of error is

.50

The sample size that guarantees all estimates of proportions will meet the margin of error requirements is computed using a planning value of p equal to

.50

Which Excel function would be used to construct a confidence interval estimate?

NORM.S.INV

In a recent poll on the Tuscaloosa News website, readers were asked if they were, "afraid of clowns". Out of 531 votes cast, 22.4% responded "Yes", and 77.6% responded "No". Which of the following best describes why you might be cautious in relying on these results?

The respondents may not be a representative sample of any population of interest.

For a given population, confidence intervals constructed from larger samples tend to be narrower than those constructed from smaller samples. Which statement below best describes why this is true?

The variability of the sample mean is less for larger samples.

Based on the confidence interval in Question #3 above, which of the following statements is most likely correct?

There is strong evidence that the machine is not properly calibrated to a mean fill-weight of 16.07 ounces.

Whenever using the t distribution in interval estimation, we must assume that

a random sample was selected

As the number of degrees of freedom for a t distribution increases, the difference between the t distribution and the standard normal distribution

becomes smaller

If the level of significance is decreased, the interval for the population proportion

becomes wider

When the level of confidence increases, the confidence interval

becomes wider

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

confidence level

As the sample size increases, the margin of error

decreases

The t distribution is a family of similar probability distributions, with each individual distribution depending on a parameter known as the _____.

degrees of freedom

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

degrees of freedom

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

interval estimate

As the degrees of freedom increase, the t distribution approaches the _____ distribution.

normal

The general form of an interval estimate of a population mean or population proportion is the _____ plus or minus the _____

point estimate, margin of error

The margin of error in an interval estimate of the population mean is a function of all of the following EXCEPT

sample mean

The degrees of freedom associated with a t distribution are a function of the

sample size

Whenever the population standard deviation is unknown, which distribution is used in developing an interval estimate for a population mean?

t distribution

The t distribution should be used whenever

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

We can reduce the margin of error in an interval estimate of p by doing any of the following EXCEPT

using a planning value p* closer to .5

The expression used to compute an interval estimate of μ may depend on any of the following factors EXCEPT

whether there is sampling error

In general, higher confidence levels provide

wider confidence intervals