Multiple Choice
Identify the
letter of the choice that best completes the statement or answers the question.


1.

If we
want to provide a 95% confidence interval for the mean of a population, the confidence coefficient
is a.  0.485  b.  1.96  c.  0.95  d.  1.645   


2.

From
a population that is not normally distributed and whose standard deviation is not known, a sample of
20 items is selected to develop an interval estimate for m. a.  The normal distribution can be used.  b.  The t
distribution with 19 degrees of freedom must be used.  c.  The t
distribution with 20 degrees of freedom must be used.  d.  The sample size
must be increased.   


3.

From
a population that is normally distributed, a sample of 25 elements is selected and the standard
deviation of the sample is computed. For the interval estimation of m, the proper
distribution to use is the a.  normal distribution  b.  t
distribution  c.  t distribution with 26 degrees of
freedom  d.  t distribution with 24 degrees of
freedom   


4.

The z
value for a 97.8% confidence interval estimation is


5.

An
interval estimate is a range of values used to estimate a.  the shape of the
population's distribution  b.  the sampling distribution  c.  a sample
statistic  d.  a population parameter   



Exhibit 82
A random sample of 81 automobiles traveling on an
interstate showed an average speed of 60 mph and a standard deviation of 13.5 mph. Assume the
distribution of speeds of all the cars is normal.


6.

Refer
to Exhibit 82. The 86.9% confidence interval for m is a.  46.500 to 73.500  b.  57.735 to
62.625  c.  59.131 to 60.869  d.  50 to
70   


7.

A
random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population
standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean
is a.  15.2 to
24.8  b.  19.200 to
20.800  c.  19.216 to 20.784  d.  21.2 to
22.8   


8.

The
sample size needed to provide a margin of error of 2 or less with a .95 probability when the
population standard deviation equals 11 is


9.

We
are interested in conducting a study in order to determine what percentage of voters of a state would
vote for the incumbent governor. What is the minimum size sample needed to estimate the population
proportion with a margin of error of 0.05 or less at 95% confidence?


10.

A
population has a mean of 150 and a standard deviation of 30. A random sample of 100 from this
population is selected. The sample has a mean of 145 and a standard deviation of 33. The sampling
error is
