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Missy Walters owns a mail-order business specializing in baby clothes. Missy is
confident the dollar amounts of all her orders are normally distributed or nearly so.
Assume she knows the mean and standard deviation are $249 and $46, respectively, for
all orders she receives.
a. Describe the sampling distribution of , where is the mean dollar-amount of an
order for a sample of 10 orders.
b. What is the probability that a simple random sample of 30 orders will provide an
estimate of the population mean dollar-amount of an order that is within plus or minus
$10 of the actual population mean?
c. What happens to the sampling distribution of when the sample size is increased
from 30 to 90? With a sample size of 90, what is the probability that will be between
$239 and $259?
The weights of items produced by a company are normally distributed with a mean of
4.5 ounces and a standard deviation of 0.3 ounces.
a. What is the probability that a randomly selected item from the production will weigh
at least 4.14 ounces?
b. What percentage of the items weighs between 4.8 and 5.04 ounces?
c. Determine the minimum weight of the heaviest 5% of all items produced.
d. If 27,875 of the items of the entire production weigh at least 5.01 ounces, how many
items have been produced?
Which of the following forecasting methods puts the least weight on the most recent
time series value?
a. exponential smoothing with = .3
b. exponential smoothing with = .2
c. moving average using the most recent 4 periods
d. moving average using the most recent 3 periods
The Video Game Supply Company (VGS) is deciding whether to set production next
year at 2,000, 2,500, or 3,000 games. Demand could be low, medium, or high. Using
historical data, VGS estimates the probabilities as 0.4 for low demand, 0.3 for medium
demand, and 0.3 for high demand. The following profit payoff table (in $100s) has been
developed:
a. Determine the expected value of each alternative and indicate what should be the
production target.
b. Determine the expected value with perfect information about the states of nature.
c. Determine the expected value of perfect information.
Exhibit 13-3
To test whether or not there is a difference between treatments A, B, and C, a sample of
12 observations has been randomly assigned to the 3 treatments. You are given the
results below.
Refer to Exhibit 13-3. The null hypothesis for this ANOVA problem is
a. 1=2
b. 1=2=3
c. 1=2=3=4
d. 1=2= ... =12
Which of the following is (are) the most common type(s) of surveys?
a. only mail surveys
b. only telephone surveys
c. only personal interviews
d. All of these answers are correct.
Exhibit 3-2
A researcher has collected the following sample data. The mean of the sample is 5.
Refer to Exhibit 3-2. The coefficient of variation is
a. 72.66%
b. 81.24%
c. 264%
d. 330%
Exhibit 9-6
A random sample of 100 people was taken. Eighty of the people in the sample favored
Candidate A. We are interested in determining whether or not the proportion of the
population in favor of Candidate A is significantly more than 75%.
Refer to Exhibit 9-6. At a .05 level of significance, it can be concluded that the
proportion of the population in favor of candidate A is
a. significantly greater than 75%
b. not significantly greater than 75%
c. significantly greater than 80%
d. not significantly greater than 80%
Exhibit 3-4
The following is the frequency distribution for the speeds of a sample of automobiles
traveling on an interstate highway.
Refer to Exhibit 3-4. The mean is
a. 35
b. 670
c. 10
d. 67
A multiple regression model has the form
= 7 + 2 x1 + 9 x2
As x1 increases by 1 unit (holding x2 constant), is expected to
a. increase by 9 units
b. decrease by 9 units
c. increase by 2 units
d. decrease by 2 units
A weighted average of the value of a random variable, where the probability function
provides weights is known as
a. a probability function
b. a random variable
c. the expected value
d. None of the answers is correct
To compute the probability that in a random sample of n elements, selected without
replacement, we will obtain x successes, we would use the
a. binomial probability distribution
b. Poisson probability distribution
c. hypergeometric probability distribution
d. exponential probability distribution
In practice, the most frequently encountered hypothesis test about a population
variance is a
a. one-tailed test, with rejection region in lower tail
b. one-tailed test, with rejection region in upper tail
c. two-tailed test, with equal-size rejection regions
d. two-tailed test, with unequal-size rejection regions
Which of the following is least useful in studying the relationship between two
variables?
a. trendline
b. stem-and-leaf display
c. crosstabulation
d. scatter diagram
In hypothesis testing, the hypothesis tentatively assumed to be true is
a. the alternative hypothesis
b. the null hypothesis
c. either the null or the alternative
d. None of the other answers are correct.
In a residual plot that does not suggest we should challenge the assumptions of our
regression model, we would expect to see
a. a horizontal band of points centered near zero
b. a widening band of points
c. a band of points having a slope consistent with that of the regression equation
d. a parabolic band of points
The complement of P(A | B) is
a. P(AC | B)
b. P(A | BC)
c. P(B | A)
d. P(A B)
The F ratio in a completely randomized ANOVA is the ratio of
a. MSTR/MSE
b. MST/MSE
c. MSE/MSTR
d. MSE/MST
If one wanted to find the probability of ten customer arrivals in an hour at a service
station, one would generally use the
a. binomial probability distribution
b. Poisson probability distribution
c. hypergeometric probability distribution
d. exponential probability distribution
