TABLE 11-8
An important factor in selecting database software is the time required for a user to
learn how to use the system. To evaluate three potential brands (A, B and C) of database
software, a company designed a test involving five different employees. To reduce
variability due to differences among employees, each of the five employees is trained
on each of the three different brands. The amount of time (in hours) needed to learn
each of the three different brands is given below:
Below is the Excel output for the randomized block design:
True or False: Referring to Table 11-8, there is evidence of a significant difference in
the mean amount of time needed to learn Brand B and Brand C at the 5% level of
significance.
TABLE 13-10
The management of a chain electronic store would like to develop a model for
predicting the weekly sales (in thousands of dollars) for individual stores based on the
number of customers who made purchases. A random sample of 12 stores yields the
following results:
True or False: Referring to Table 13-10, the p-value of the t test and F test should be the
same when testing whether the number of customers who make purchases is a good
predictor for weekly sales.
True or False: TABLE 19-6
A student wanted to find out the optimal strategy to study for a Business Statistics
exam. He constructed the following payoff table based on the mean amount of time he
needed to study every week for the course and the degree of difficulty of the exam.
From the information that he gathered from students who had taken the course, he
concluded that there was a 40% probability that the exam would be easy.
Referring to Table 19-6, the optimal strategy using the maximax criterion is to study 8
hours per week on average for the exam.
True or False: The Guidelines for Developing Visualizations recommend avoiding
uncommon chart types such as doughnut, radar, cone and pyramid charts.
True or False: Whether the university is private or public is an example of a categorical
variable.
True or False: When constructing a frequency distribution, classes should be selected so
that they are of equal width.
True or False: For all two-sample tests, the sample sizes must be equal in the two
groups.
True or False: The t distribution is used to construct confidence intervals for the
population mean when the population standard deviation is unknown.
True or False: The C in the DCOVA framework stands for “collect.”
TABLE 17-8
The superintendent of a school district wanted to predict the percentage of students
passing a sixth-grade proficiency test. She obtained the data on percentage of students
passing the proficiency test (% Passing), daily mean of the percentage of students
attending class (% Attendance), mean teacher salary in dollars (Salaries), and
instructional spending per pupil in dollars (Spending) of 47 schools in the state.
Following is the multiple regression output with Y = % Passing as the dependent
variable, X1 = % Attendance, X2 = Salaries and X3 = Spending:
Referring to Table 17-8, which of the following is the correct null hypothesis to test
whether the daily mean of the percentage of students attending class has any effect on
the percentage of students passing the proficiency test, taking into account the effect of
all the other independent variables?
A) H0 : β0 = 0
B) H0 : β1 = 0
C) H0 : β2 = 0
D) H0 : β3 = 0
Which of the following is a method for breaking process into a series of steps in order
to eliminate defects and produce near perfect results?
A) Deming’s 14 points management
B) Six Sigma management
C) Shewhart-Deming cycle
D) R chart and chart
A sample of 100 fuses from a very large shipment is found to have 10 that are defective.
Based on this information, which of the following will you construct to learn about the
proportion of fuses that are defective?
A) Confidence interval estimate for the total using the Student’s t distribution
B) Confidence interval estimate for the mean using the Student’s t distribution
C) Confidence interval estimate for the proportion using the standard normal
distribution
D) Confidence interval estimate for the difference between two means using the
standard normal distribution
A dummy variable is used as an independent variable in a regression model when
A) the variable involved is numerical.
B) the variable involved is categorical.
C) a curvilinear relationship is suspected.
D) when 2 independent variables interact.
If you know that the probability of committing a Type II error ( ) is 5%, you can tell
that the power of the test is
A) 2.5%.
B) 95%.
C) 97.5%.
D) unknown.
Since a ________ is not a randomly selected probability sample, there is no way to
know how well it represents the overall population.
A) simple random sample
B) convenience sample
C) stratified sample
D) cluster sample
TABLE 17-10
Given below are results from the regression analysis where the dependent variable is
the number of weeks a worker is unemployed due to a layoff (Unemploy) and the
independent variables are the age of the worker (Age), the number of years of education
received (Edu), the number of years at the previous job (Job Yr), a dummy variable for
marital status (Married: 1 = married, 0 = otherwise), a dummy variable for head of
household (Head: 1 = yes, 0 = no) and a dummy variable for management position
(Manager: 1 = yes, 0 = no). We shall call this Model 1. The coefficient of partial
determination ( ) of each of the 6 predictors are, respectively,
0.2807, 0.0386, 0.0317, 0.0141, 0.0958, and 0.1201.
Model 2 is the regression analysis where the dependent variable is Unemploy and the
independent variables are Age and Manager. The results of the regression analysis are
given below:
Referring to Table 17-10, Model 1, which of the following is a correct statement?
A) On average, a worker who is a year older is estimated to stay jobless longer by
approximately 32.66 weeks while holding constant the effects of all the remaining
independent variables.
B) On average, a worker who is a year older is estimated to stay jobless longer by
approximately 1.29 weeks while holding constant the effects of all the remaining
independent variables.
C) On average, a worker who is a year older is estimated to stay jobless shorter by
approximately 1.35 weeks while holding constant the effects of all the remaining
independent variables.
D) On average, a worker who is a year older is estimated to stay jobless longer by
approximately 0.62 weeks while holding constant the effects of all the remaining
independent variables.
TABLE 17-9
What are the factors that determine the acceleration time (in sec.) from 0 to 60 miles per
hour of a car? Data on the following variables for 171 different vehicle models were
collected:
Accel Time: Acceleration time in sec.
Cargo Vol: Cargo volume in cu. ft.
HP: Horsepower
MPG: Miles per gallon
SUV: 1 if the vehicle model is an SUV with Coupe as the base when SUV and Sedan
are both 0
Sedan: 1 if the vehicle model is a sedan with Coupe as the base when SUV and Sedan
are both 0
The regression results using acceleration time as the dependent variable and the
remaining variables as the independent variables are presented below.
The various residual plots are as shown below.
The coefficient of partial determination ( ) of each of the 5
predictors are, respectively, 0.0380, 0.4376, 0.0248, 0.0188, and 0.0312.
The coefficient of multiple determination for the regression model using each of the 5
variables Xj as the dependent variable and all other X variables as independent variables
( ) are, respectively, 0.7461, 0.5676, 0.6764, 0.8582, 0.6632.
Referring to Table 17-9, which of the following assumptions is most likely violated
based on the residual plot for HP?
A) Linearity
B) Normality of errors
C) Independence of errors
D) None of the above
If an economist wishes to determine whether there is evidence that mean family income
in a community equals $50,000,
A) either a one-tail or two-tail test could be used with equivalent results.
B) a one-tail test should be utilized.
C) a two-tail test should be utilized.
D) None of the above.
Suppose the ages of students in Statistics 101 follow a right skewed distribution with a
mean of 23 years and a standard deviation of 3 years. If we randomly sampled 100
students, which of the following statements about the sampling distribution of the
sample mean age is incorrect?
A) The mean of the sampling distribution is equal to 23 years.
B) The standard deviation of the sampling distribution is equal to 3 years.
C) The shape of the sampling distribution is approximately normal.
D) The standard error of the sampling distribution is equal to 0.3 years.
At US Data Corporation’s website, they advertised that “Because of our commitment to
quality and our vast amount of industry knowledge and experience, we have grown to
be one of America’s leading providers of mailing lists, marketing data, sales leads and
research data. We maintain databases of information on consumers and businesses
nationwide that set industry standards for mission critical currency, reliability and
accuracy.” Trying to reach 500 potential donors for their annual phone donation
campaign, a local fire department purchased a list of donors from the company. This list
is an example of a
A) stratified sample.
B) systematic sample.
C) judgment sample.
D) frame.
If we know that the length of time it takes a college student to find a parking spot in the
library parking lot follows a normal distribution with a mean of 3.5 minutes and a
standard deviation of 1 minute, find the probability that a randomly selected college
student will find a parking spot in the library parking lot in less than 3 minutes.
A) 0.3551
B) 0.3085
C) 0.2674
D) 0.1915
TABLE 17-6
A weight-loss clinic wants to use regression analysis to build a model for weight loss of
a client (measured in pounds). Two variables thought to affect weight loss are client’s
length of time on the weight-loss program and time of session. These variables are
described below:
Y = Weight loss (in pounds)
X1 = Length of time in weight-loss program (in months)
X2 = 1 if morning session, 0 if not
X3 = 1 if afternoon session, 0 if not (Base level = evening session)
Data for 12 clients on a weight-loss program at the clinic were collected and used to fit
the interaction model:
Y = β0 + β1X1 + β2X2 + β3X3 + β4X1X2 + β5X1X3 + ε
Partial output from Microsoft Excel follows:
Regression Statistics
ANOVA
F = 5.41118 Significance F = 0.040201
Referring to Table 17-6, which of the following statements is supported by the analysis
shown?
A) There is sufficient evidence (at α = 0.05) of curvature in the relationship between
weight loss (Y) and months in program (X1).
B) There is sufficient evidence (at α = 0.05) to indicate that the relationship between
weight loss (Y) and months in program (X1) depends on session time.
C) There is sufficient evidence (at α = 0.10) to indicate that the session time (morning,
afternoon, evening) affects weight loss (Y).
D) There is insufficient evidence (at α = 0.10) to indicate that the relationship between
weight loss (Y) and months in program (X1) depends on session time.
TABLE 17-3
A financial analyst wanted to examine the relationship between salary (in $1,000) and 4
variables: age (X1 = Age), experience in the field (X2 = Exper), number of degrees (X3 =
Degrees), and number of previous jobs in the field (X4 = Prevjobs). He took a sample of
20 employees and obtained the following Microsoft Excel output:
SUMMARY OUTPUT
Regression Statistics
ANOVA
Referring to Table 17-3, the analyst wants to use an F-test to test H0 : β1 = β2 = β3 = β4
= 0. The appropriate alternative hypothesis is ________.
TABLE 11-11
A student team in a business statistics course designed an experiment to investigate
whether the brand of bubblegum used affected the size of bubbles they could blow. To
reduce the person-to-person variability, the students decided to use a randomized block
design using themselves as blocks.
Four brands of bubblegum were tested. A student chewed two pieces of a brand of gum
and then blew a bubble, attempting to make it as big as possible. Another student
measured the diameter of the bubble at its biggest point. The following table gives the
diameters of the bubbles (in inches) for the 16 observations.
Referring to Table 11-11, what is the p-value of the F test statistic for testing the block
effects?
TABLE 5-5
From an inventory of 48 new cars being shipped to local dealerships, corporate reports
indicate that 12 have defective radios installed.
Referring to Table 5-5, what is the probability out of the 8 new cars it just received that,
when each is tested, no more than 2 of the cars have defective radios?
TABLE 7-4
According to a survey, only 15% of customers who visited the website of a major retail
store made a purchase. Random sample sizes of 50 are selected.
Referring to Table 7-4, 90% of the samples will have less than what percentage of
customers who will make a purchase after visiting the website?
TABLE 11-4
An agronomist wants to compare the crop yield of 3 varieties of chickpea seeds. She
plants 15 fields, 5 with each variety. She then measures the crop yield in bushels per
acre. Treating this as a completely randomized design, the results are presented in the
table that follows.
Referring to Table 11-4, using an overall level of significance of 0.01, the critical value
of the Studentized range Q used in calculating the critical range for the Tukey-Kramer
procedure is ________.
TABLE 17-8
The superintendent of a school district wanted to predict the percentage of students
passing a sixth-grade proficiency test. She obtained the data on percentage of students
passing the proficiency test (% Passing), daily mean of the percentage of students
attending class (% Attendance), mean teacher salary in dollars (Salaries), and
instructional spending per pupil in dollars (Spending) of 47 schools in the state.
Following is the multiple regression output with Y = % Passing as the dependent
variable, X1 = % Attendance, X2 = Salaries and X3 = Spending:
Referring to Table 17-8, what are the lower and upper limits of the 95% confidence
interval estimate for the effect of a one dollar increase in mean teacher salary on the
mean percentage of students passing the proficiency test?