In hypothesis testing if the null hypothesis has been rejected when the alternative
hypothesis has been true,
a. a Type I error has been committed
b. a Type II error has been committed
c. either a Type I or Type II error has been committed
d. the correct decision has been made
The weight of a .5 cubic yard bag of landscape mulch is uniformly distributed over the
interval from 38.5 to 41.5 pounds.
a. Give a mathematical expression for the probability density function.
b. What is the probability that a bag will weigh more than 40 pounds?
c. What is the probability that a bag will weigh less than 39 pounds?
d. What is the probability that a bag will weigh between 39 and 40 pounds?
Exhibit 2-4
A survey of 400 college seniors resulted in the following crosstabulation regarding their
undergraduate major and whether or not they plan to go to graduate school.
Refer to Exhibit 2-4. What percentage of the students’ undergraduate major is
engineering?
a. 292
b. 520
c. 65
d. 36.5
Exhibit 12-1
When individuals in a sample of 150 were asked whether or not they supported capital
punishment, the following information was obtained.
We are interested in determining whether or not the opinions of the individuals (as to
Yes, No, and No Opinion) are uniformly distributed.
Refer to Exhibit 12-1. The expected frequency for each group is
a. 0.333
b. 0.50
c. 1/3
d. 50
The actual demand for a product and the forecast for the product are shown below.
Calculate MAD and MSE. Show all of your computations.
Which of the following is NOT a scale of measurement?
a. nominal
b. ordinal
c. interval
d. All of these are scales of measurement.
Exhibit 10-1
Salary information regarding male and female employees of a large company is shown
below.
Refer to Exhibit 10-1. The 95% confidence interval for the difference between the
means of the two populations is
a. 0 to 6.92
b. -2 to 2
c. -1.96 to 1.96
d. -0.92 to 6.92
“D” size batteries produced by MNM Corporation have had a life expectancy of 87
hours. Because of an improved production process, the company believes that there has
been an increase in the life expectancy of its “D” size batteries. A sample of 36 batteries
showed an average life of 88.5 hours. Assume from past information that it is known
that the standard deviation of the population is 9 hours.
A random sample of 121 checking accounts at a bank showed an average daily balance
of $280. The population standard deviation is known to be $60.
a. Is it necessary to know anything about the shape of the distribution of the account
balances in order to make an interval estimate of the mean of all the account balances?
Explain.
b. Find the standard error of the mean.
c. Give a point estimate of the population mean.
d. Construct a 95% confidence interval estimate for the population mean.
e. Interpret the confidence interval estimate that you constructed in part d.
Simple random sampling has been used to obtain a sample of 81 elements from a
population of size 500. The sample mean is 120, and the sample standard deviation is
determined to be 36.
a. Estimate the standard error of the mean.
b. Develop an approximate 95% confidence interval for the population mean.
c. Estimate the population total.
d. Develop an approximate 95% confidence interval for the population total.
When the rejection region is in the lower tail of the sampling distribution, the p-value is
the area under the curve
a. less than or equal to the critical value
b. less than or equal to the test statistic
c. greater than or equal to the critical value
d. greater than or equal to the test statistic
Suppose annual salaries for sales associates from a particular store have a mean of
$32,500 and a standard deviation of $2,500.
a. Calculate and interpret the z-score for a sales associate who makes $36,000.
b. Use Chebyshev’s theorem to calculate the percentage of sales associates with salaries
between $26,250 and $38,750.
c. Suppose that the distribution of annual salaries for sales associates at this store is
bell-shaped. Use the empirical rule to calculate the percentage of sales associates with
salaries between $27,500 and $37,500.
d. Use the empirical rule to determine the percentage of sales associates with salaries
less than $27,500.
e. Still suppose that the distribution of annual salaries for sales associates at this store is
bell-shaped. A sales associate makes $42,000. Should this salary be considered an
outlier? Explain.
Exhibit 10-2
The following information was obtained from matched samples.
The daily production rates for a sample of workers before and after a training program
are shown below.
Refer to Exhibit 10-2. Based on the results of question 18, the
a. null hypothesis should be rejected
b. null hypothesis should not be rejected
c. alternative hypothesis should be accepted
d. None of these alternatives is correct.
Del Michaels had a successful morning, or so he thinks, selling 1300 surplus notebook
computers over the telephone to three commercial customers. The three customers were
not equally skillful at negotiating a low unit price. Customer A bought 600 computers
for $1252 each, B bought 300 units at $1310 each, and C bought 400 at $1375 each.
a. What is the average unit price at which Del sold the 1300 computers?
b. Del’s manager told Del he expected him to sell, by the end of the day, a total of 2500
surplus computers at an average price of $1312 each. What is the average unit price at
which Del must sell the remaining 1200 computers?
Excel’s __________ function can be used to compute the expected value of a discrete
random variable.
a. SUMPRODUCT
b. AVERAGE
c. MEDIAN
d. VAR
In an experiment, events A and B are mutually exclusive. If P(A) 0.6, then the
probability of B
a. cannot be larger than 0.4
b. can be any value greater than 0.6
c. can be any value between 0 to 1
d. cannot be determined with the information given
The uncontrollable future events that can affect the outcome of a decision are known as
a. alternatives
b. decision outcome
c. payoff
d. states of nature
Do the following data indicate that the variance of the population from which this
sample has been drawn is significantly more than 12? Use = 0.05.
The manager of Hudson Auto Repair wants to advertise one price for an engine tune-up,
with parts included. Before he decides the price to advertise, he needs a good estimate
of the average cost of tune-up parts. A sample of 20 customer invoices for tune-ups has
been taken and the costs of parts, rounded to the nearest dollar, are listed below.
Provide a 90% confidence interval estimate of the mean cost of parts per tune-up for all
of the tune-ups performed at Hudson Auto Repair.
Two classes in business statistics showed the following results on a recent test.
Carry out a test to determine whether the difference in the variance of the scores on this
test is due to chance variation or is statistically significant with a .02 level of
significance.
The following shows the monthly sales in units of six salespersons before and after a
bonus plan was introduced. At 95% confidence, determine whether the bonus plan has
increased sales significantly. (For the following matched samples, let the difference “d”
be: d = after – before.)
From the courthouse records, it is found that in 60 divorce cases, the filing for divorce
was initiated by the wife 41 times. Using the sign test, test for a difference in filing
between husband and wives. Let = 0.05
In a regression analysis involving 18 observations and four independent variables, the
following information was obtained.
Multiple R = 0.6000
R Square = 0.3600
Standard Error = 4.8000
Based on the above information, fill in all the blanks in the following ANOVA table.
