14.
A study of college football games shows that the number of holding penalties assessed has a mean of
2.3 penalties per game and a standard deviation of 1.1 penalties per game. What is the probability that,
for a sample of 40 college games to be played next week, the mean number of holding penalties will be
2.05 penalties per game or more?
15.
Let Z be a standard normal random variable. Use the calculator provided to determine the value of
C such that =P≤−c≤Zc0.9534.
Carry your intermediate computations to at least four decimal places. Round your answer to at least two
decimal places.
16.
A laboratory in Alaska is interested in finding the mean chloride level for a healthy resident in the state.
A random sample of 70 healthy residents has a mean chloride level of 102mEq/L. If it is known that the
chloride levels in healthy individuals residing in Alaska have a standard deviation of 38mEq/L, find a 90%
confidence interval for the true mean chloride level of all healthy Alaska residents. Then complete the
table below.
Carry your intermediate computations to at least three decimal places. Round your answers to one
decimal place.
17.
•
•
Consider a t distribution with
degrees of freedom.
Compute
decimal places.
. Round your answer to at least three
Consider a t distribution with
degrees of freedom. Find the value
of such that
decimal places.
. Round your answer to at least three
18.
19.
20.
21.
22.
A random selection of volunteers at a research institute have been exposed to
a typical cold virus. After they started to have cold symptoms,
were given multivitamin tablets daily which contain
of them
grams of vitamin C and
various other vitamins and minerals. The remaining
volunteers were given
placebo tablets. For each individual, the length of time taken to recover from
cold is recorded. At the end of the experiment following data are obtained:
Days to recover from cold
Treated
with
multivita
min
Treated
with
placebo
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
Send data
to Excel
It is known that the population standard deviation of recovery time from cold
is
days when treated with multivitamin, and the population standard
deviation of recovery time from cold is
days when treated with placebo
tablets. It is also known that both populations are approximately normally
distributed. The researchers claim that the mean recovery time,
, of the
patients treated with multivitamin is not equal to the mean recovery time
,
of the patients who are treated with placebo tablets. At the
level of
significance, is there enough evidence to support this claim? Perform a twotailed test. Then fill in the table below.
Carry your intermediate computations to at least three decimal places and
round your answers as specified in the table. (If necessary, consult a list of
formulas.)
23.
24.
Might we be able to predict life expectancies from birthrates?
Below are bivariate data giving birthrate and life expectancy information for
each of twelve countries. For each of the countries, both
, the number of
births per one thousand people in the population, and , the female life
expectancy (in years), are given. Also shown are the scatter plot for the data
and the least-squares regression line. The equation for this line
is
.
25.
An advertising firm wishes to demonstrate to its clients the effectiveness of the
advertising campaigns it has conducted. The following bivariate data on
twelve recent campaigns, including the cost of each campaign (denoted by ,
in millions of dollars) and the resulting percentage increase in sales (denoted
by ) following the campaign, were presented by the firm. A scatter plot of the
data is shown in Figure 1. Also given are the products of the values for
campaign cost and values for percentage increase in sales for each of the
twelve campaigns. (These products, written in the column labelled "
aid in calculations.)
," may
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