Chapter 7

Question 1

Population parameters are

Answer 1

the actual percentage
of Americans who identify as environmentalists or the actual average level of education in
the United States.

Question 2

Why estimate? T

Answer 2

The goal of most research is to find the population parameter. Yet we hardly
ever have enough resources to collect information about the entire population. We rarely
know the actual value of the population parameter. On the other hand, we can learn a lot
about a population by randomly selecting a sample from that population and obtaining an
estimate of the population parameter. T

Question 3

The major objective of sampling theory and

statistical inference is

Answer 3

to provide estimates of unknown population parameters from sample
statistics.

Question 4

Estimation A

Answer 4

A process whereby we select a random sample from a population and use a sample statistic to
estimate a population parameter.

Question 5

point estimate

Answer 5

A sample statistic used to estimate the exact value of a population parameter

Question 6

Confidence interval (CI)

Answer 6

A range of values defined by the confidence level within which the population
parameter is estimated to fall. A confidence interval may also be referred to as a margin of error.

Question 7

Confidence level

Answer 7

The likelihood, expressed as a percentage or a probability, that a specified interval will
contain the population parameter.

Question 8

The problem with point estimates is that

Answer 8

sample statistics vary, usually resulting in some

sort of sampling error.

Question 9

. In interval estimation,

Answer 9

we identify a range of values within which the population

parameter may fall.

Question 10

margin of error

Answer 10

The radius of a confidence interval

Question 11

Note that to calculate a confidence interval,

Answer 11

we take the sample mean and add to or

subtract from it the product of a Z value and the standard error

Question 12

The Z value corresponding to a 95% confidence

level is

Answer 12

1.96.

Question 13

The confidence interval is calculated by adding to

Answer 13

and subtracting from the observed

sample mean the product of the standard error and Z:

Question 14

We can be 95% confident that the actual mean hours spent watching television by
Americans from which the GSS sample was taken is not less than 2.78 hours and not
greater than 3.10 hours. In other words, if we drew a large number of samples (N = 1,001)
from this population,

Answer 14

then 95 times out of 100, the true population mean would be

included within our computed interval.

Question 15

. We will have to consider two factors to meet

the assumption of normality with the sampling distribution of proportions:

Answer 15

(1) the sample
size N and (2) the sample proportions p and 1 − p. When p and 1 − p are about 0.50, a
sample size of at least 50 is sufficient. But when p > 0.50 (or 1 − p < 0.50), a larger sample
is required to meet the assumption of normality.

Question 16

what size is typically good for any one estimeate of a pop prop

Answer 16

Usually, a sample of 100 or more is

adequate for any single estimate of a population proportion

Question 17

We are 95% confident that the true population proportion is somewhere between 0.38 and
0.46. In other words, if we drew a large number of samples from the population of adults,
then 95 times out of 100, the confidence interval we obtained would contain the

Answer 17

true
population proportion. We can also express this result in percentages and say that we are
95% confident that the true population percentage of Americans who identify as
environmentalists is between 38% and 46%.

Question 18

When using the 99% confidence interval, we can be almost certain

Answer 18

(99 times out of 100)
that the true population proportion is included in the interval ranging from .37 to .47 (or
37% to 47%).

Question 19

When estimates are reported for subgroups, the confidence intervals are likely to vary. Even
when a confidence interval is reported only for the overall sample, we can easily compute

Answer 19

separate confidence intervals for each of the subgroups if the confidence level and the size of
each of the subgroups are included.

Question 20

The goal of most research is to find

Answer 20

population parameters. The major objective of sampling theory
and statistical inference is to provide estimates of unknown parameters from sample statistics

Question 21

Researchers make point estimates and interval estimates. Point estimates are

Answer 21

sample statistics used to
estimate the exact value of a population parameter. Interval estimates are ranges of values within
which the population parameter may fall

Question 22

Confidence intervals can be used to estimate

Answer 22

population parameters such as means or proportions.
Their accuracy is defined with the confidence level. The most common confidence levels are 90%,
95%, and 99%

Question 23

To establish a confidence interval for a mean or a proportion,

Answer 23

add or subtract from the mean or the

proportion the product of the standard error and the Z value corresponding to the confidence level.