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# 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
0.95
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
0.9
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
decreases
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
n-1
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.