STAT 121 FINAL EXAM QUESTIONS WITH VERIFIED
ANSWERS
A study investigated whether a student's grade in STAT 121 could be predicted from
their ACT math score. What are the response and explanatory variables?
a) resp = stat grade
expl. = ACT math
b) resp = ACT math
expl = stat grade - Answers - a) resp = stat grade
expl. = ACT math
What is the visual display tool for a Q --> Q case? - Answers - scatterplot
What are the numerical study tools for a Q --> Q case? - Answers - correlation,
regression line
What are the goals for a Q --> Q case? - Answers - characterize the nature of the
relationship
predict one variable from another
investigate if changes in one variable cause changes in another
If a data set consists of 2 variables measured on each of 20 individuals, how many dots
are in the scatterplot?
a) 10
b) 20
c) 30
d) 40 - Answers - b) 20
What are the 3 ways to assess a scatterplot? - Answers - direction
form
strength
What are the 3 classes or ways you can categorize the form of a given scatterplot? -
Answers - linear
nonlinear
non-distinguishable
What is considered an outlier? - Answers - any point that doesn't follow the relationship
or form in the data
,T or F: Everyone will draw the same conclusions about form, direction, and strength
from a scatter plot? - Answers - FALSE
T or F: a Q --> Q relationship only works for linear relationships? - Answers - TRUE
In a linear relationship you need a measure of strength that is ________ , __________ ,
and ______________ . - Answers - objective
numeric
not fooled by scales of information
What is the symbol for correlation coefficient? - Answers - r
What is the correlation coefficient? - Answers - a numeric, scale invariant measure of
strength and direction of linear relationship between 2 quantitative variables
T or F: a numeric, scale invariant measure of strength and direction of a relationship
between 2 quantitative variables ONLY works for a linear relationship - Answers - TRUE
In order for their to be a perfect negative relationship (in a Q --> Q case )what needs to
be the case? - Answers - EVERY SINGLE point needs to fall exactly on the negative
slope line
In order for their to be a perfect positive relationship (in a Q --> Q case )what needs to
be the case? - Answers - EVERY SINGLE point needs to fall exactly on the positive
slope line
In order for their to be an intermediate negative relationship (in a Q --> Q case )what
needs to be the case? - Answers - points will be more spread out on the negative slope
In order for their to be an intermediate positive relationship (in a Q --> Q case )what
needs to be the case? - Answers - points will be more spread out on the positive slope
What does it mean when r = 0? - Answers - there is no linear relationship
What does it mean when r > -1, but < 0? - Answers - intermediate negative relationship
What does it mean when r > 0 but < 1? - Answers - intermediate positive relationship
What does it mean when r = 1? - Answers - perfect positive relationship
What does it mean when r = -1? - Answers - perfect negative relationship
Which numbers will the value of r always fall between? - Answers - 1 & -1
What are the properties of r? - Answers - ranges between 1 & -1
,NO units of measurement
when the units of measurement change for either of the variables, the value of r does
not change
NO distinction between response and explanatory variable
heavily influenced by outliers
What are the following properties attached to?
ranges between 1 & -1
NO units of measurement
when the units of measurement change for either of the variables, the value of r does
not change
NO distinction between response and explanatory variable
heavily influenced by outliers - Answers - r
Which of the following statements is true?
a) r works for quantitative or categorical variables
b) r makes a distinction between explanatory and response variables
c) sing of r denotes direction of relationship
d) r could be -1.5 - Answers - c) sing of r denotes direction of relationship
T or F: r ONLY works for quantitative variables - Answers - TRUE
Which of the following statements is true?
a) r can be used to describe the strength of curved relationships
b) r is resistant to outliers
c) r does not change if the units of x or y change
d) r is a complete summary of 2-variable data - Answers - c) r does not change if the
units of x or y change
Which of the following statements is false?
a) r cannot be used to describe the strength of curved relationships
b) r is affected by outliers
c) r does not change if the units of x or y change
d) r is a complete summary of 2-variable data - Answers - d) r is a complete summary of
2-variable data
What adds a measure of strength of the relationship in a Q-->Q relationship? - Answers
- r - correlation coefficient
, For the data displayed in the following scatterplot, is it appropriate to calculate the
correlation?
image A
A. Yes, because the data is bivariate.
B. Yes, because the relationship is linear.
C. No, because the sample size is not large enough.
D. No, because the relationship does not appear linear. - Answers - B. Yes, because
the relationship is linear.
Referring to question 1, how would you describe the form, direction, and strength of the
scatterplot?
image A
A. Linear, negative, moderately strong
B. Linear, positive, moderately strong
C. Non-linear, negative, weak
D. Non-linear, positive, weak
E. Linear, negative, weak
F. Linear, positive, weak - Answers - A. Linear, negative, moderately strong
True or False: If the correlation between x and y is r = 0, then we can say that there is
no relationship of any form between x and y. - Answers - FALSE
True or False: The correlation between x and y equals the correlation between y and x
(i.e., changing the roles of x and y does not change r). - Answers - TRUE
True or False: Values of correlation, r, close to -1.0 indicate weak linear relationships
and values close to +1.0 indicate strong linear relationships. - Answers - FALSE
Coffee is a leading export from several developing countries. When coffee prices are
high, farmers often clear forest to plant more coffee trees. Here are five years' data on
prices paid to coffee growers in Indonesia and the percent of forest lost in a national
park that lies in a coffee-producing region:
image B
How would you describe the relationship between price and percent of forest lost?
Construct a scatterplot to answer the question.
A. A negative linear relationship
B. There is no recognizable pattern between price and percent of forest lost.
C. A positive linear relationship.
ANSWERS
A study investigated whether a student's grade in STAT 121 could be predicted from
their ACT math score. What are the response and explanatory variables?
a) resp = stat grade
expl. = ACT math
b) resp = ACT math
expl = stat grade - Answers - a) resp = stat grade
expl. = ACT math
What is the visual display tool for a Q --> Q case? - Answers - scatterplot
What are the numerical study tools for a Q --> Q case? - Answers - correlation,
regression line
What are the goals for a Q --> Q case? - Answers - characterize the nature of the
relationship
predict one variable from another
investigate if changes in one variable cause changes in another
If a data set consists of 2 variables measured on each of 20 individuals, how many dots
are in the scatterplot?
a) 10
b) 20
c) 30
d) 40 - Answers - b) 20
What are the 3 ways to assess a scatterplot? - Answers - direction
form
strength
What are the 3 classes or ways you can categorize the form of a given scatterplot? -
Answers - linear
nonlinear
non-distinguishable
What is considered an outlier? - Answers - any point that doesn't follow the relationship
or form in the data
,T or F: Everyone will draw the same conclusions about form, direction, and strength
from a scatter plot? - Answers - FALSE
T or F: a Q --> Q relationship only works for linear relationships? - Answers - TRUE
In a linear relationship you need a measure of strength that is ________ , __________ ,
and ______________ . - Answers - objective
numeric
not fooled by scales of information
What is the symbol for correlation coefficient? - Answers - r
What is the correlation coefficient? - Answers - a numeric, scale invariant measure of
strength and direction of linear relationship between 2 quantitative variables
T or F: a numeric, scale invariant measure of strength and direction of a relationship
between 2 quantitative variables ONLY works for a linear relationship - Answers - TRUE
In order for their to be a perfect negative relationship (in a Q --> Q case )what needs to
be the case? - Answers - EVERY SINGLE point needs to fall exactly on the negative
slope line
In order for their to be a perfect positive relationship (in a Q --> Q case )what needs to
be the case? - Answers - EVERY SINGLE point needs to fall exactly on the positive
slope line
In order for their to be an intermediate negative relationship (in a Q --> Q case )what
needs to be the case? - Answers - points will be more spread out on the negative slope
In order for their to be an intermediate positive relationship (in a Q --> Q case )what
needs to be the case? - Answers - points will be more spread out on the positive slope
What does it mean when r = 0? - Answers - there is no linear relationship
What does it mean when r > -1, but < 0? - Answers - intermediate negative relationship
What does it mean when r > 0 but < 1? - Answers - intermediate positive relationship
What does it mean when r = 1? - Answers - perfect positive relationship
What does it mean when r = -1? - Answers - perfect negative relationship
Which numbers will the value of r always fall between? - Answers - 1 & -1
What are the properties of r? - Answers - ranges between 1 & -1
,NO units of measurement
when the units of measurement change for either of the variables, the value of r does
not change
NO distinction between response and explanatory variable
heavily influenced by outliers
What are the following properties attached to?
ranges between 1 & -1
NO units of measurement
when the units of measurement change for either of the variables, the value of r does
not change
NO distinction between response and explanatory variable
heavily influenced by outliers - Answers - r
Which of the following statements is true?
a) r works for quantitative or categorical variables
b) r makes a distinction between explanatory and response variables
c) sing of r denotes direction of relationship
d) r could be -1.5 - Answers - c) sing of r denotes direction of relationship
T or F: r ONLY works for quantitative variables - Answers - TRUE
Which of the following statements is true?
a) r can be used to describe the strength of curved relationships
b) r is resistant to outliers
c) r does not change if the units of x or y change
d) r is a complete summary of 2-variable data - Answers - c) r does not change if the
units of x or y change
Which of the following statements is false?
a) r cannot be used to describe the strength of curved relationships
b) r is affected by outliers
c) r does not change if the units of x or y change
d) r is a complete summary of 2-variable data - Answers - d) r is a complete summary of
2-variable data
What adds a measure of strength of the relationship in a Q-->Q relationship? - Answers
- r - correlation coefficient
, For the data displayed in the following scatterplot, is it appropriate to calculate the
correlation?
image A
A. Yes, because the data is bivariate.
B. Yes, because the relationship is linear.
C. No, because the sample size is not large enough.
D. No, because the relationship does not appear linear. - Answers - B. Yes, because
the relationship is linear.
Referring to question 1, how would you describe the form, direction, and strength of the
scatterplot?
image A
A. Linear, negative, moderately strong
B. Linear, positive, moderately strong
C. Non-linear, negative, weak
D. Non-linear, positive, weak
E. Linear, negative, weak
F. Linear, positive, weak - Answers - A. Linear, negative, moderately strong
True or False: If the correlation between x and y is r = 0, then we can say that there is
no relationship of any form between x and y. - Answers - FALSE
True or False: The correlation between x and y equals the correlation between y and x
(i.e., changing the roles of x and y does not change r). - Answers - TRUE
True or False: Values of correlation, r, close to -1.0 indicate weak linear relationships
and values close to +1.0 indicate strong linear relationships. - Answers - FALSE
Coffee is a leading export from several developing countries. When coffee prices are
high, farmers often clear forest to plant more coffee trees. Here are five years' data on
prices paid to coffee growers in Indonesia and the percent of forest lost in a national
park that lies in a coffee-producing region:
image B
How would you describe the relationship between price and percent of forest lost?
Construct a scatterplot to answer the question.
A. A negative linear relationship
B. There is no recognizable pattern between price and percent of forest lost.
C. A positive linear relationship.
