Stats Chapter 8 Interval Estimation

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The absolute value of the difference between the point estimate and the population parameter it estimates is:

the sampling error

When s is used to estimate σ, the margin of error is computed by using

t distribution

If we want to provide a 95% confidence interval for the mean of a population, the confidence coefficient is


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

For the interval estimation of μ when σ is known and the sample is large, the proper distribution to use is

the normal distribution

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

interval estimate

The value added and subtracted from a point estimate in order to develop an interval estimate of the population parameter is known as the

margin of error

If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be


Whenever the population standard deviation is unknown and the population has a normal or near-normal distribution, which distribution is used in developing an interval estimation?

t distribution

In interval estimation, the t distribution is applicable only when

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

In developing an interval estimate, if the population standard deviation is unknown

the sample standard deviation can be used

In order to use the normal distribution for interval estimation of μ when σ is known and the sample is very small, the population

must have a normal distribution

From a population that is not normally distributed and whose standard deviation is not known, a sample of 6 items is selected to develop an interval estimate for the mean of the population (μ).

The sample size must be increased.

A sample of 200 elements from a population with a known standard deviation is selected. For an interval estimation of μ, the proper distribution to use is the

normal distribution

As the sample size increases, the margin of error


For which of the following values of P is the value of P(1 - P) maximized?

a. P = 0.99
b. P = 0.90
c. P = 0.01
d. P = 0.50

P = 0.50

A 95% confidence interval for a population mean is determined to be 100 to 120. If the confidence coefficient is reduced to 0.90, the interval for μ

becomes narrower

Using an α = 0.04 a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion

becomes wider

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

confidence level

After computing a confidence interval, the user believes the results are meaningless because the width of the interval is too large. Which one of the following is the best recommendation?

Increase the sample size.

If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect

the size of the confidence interval to increase

In general, higher confidence levels provide

wider confidence intervals

An interval estimate is a range of values used to estimate

a population parameter

In determining the sample size necessary to estimate a population proportion, which of the following information is not needed?

the mean of the population

Whenever using the t distribution for interval estimation (when the sample size is very small), we must assume that

the population is approximately normal

A sample of 20 items from a population with an unknown σ is selected in order to develop an interval estimate of μ. Which of the following is not necessary?

The sample must have a normal distribution.

When the level of confidence decreases, the margin of error

becomes smaller

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


Which of the following best describes the form of the sampling distribution of the sample proportion?

It is approximately normal as long as np 5 and n(1-p) 5.

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