STAT 121 final exam Revision Questions 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
a) resp = stat grade
expl. = ACT math
What is the visual display tool for a Q --> Q case?
scatterplot
What are the numerical study tools for a Q --> Q case?
correlation, regression line
What are the goals for a Q --> Q case?
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
b) 20
What are the 3 ways to assess a scatterplot?
direction
form
strength
,What are the 3 classes or ways you can categorize the form of a given scatterplot?
linear
nonlinear
non-distinguishable
What is considered an outlier?
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?
FALSE
T or F: a Q --> Q relationship only works for linear relationships?
TRUE
In a linear relationship you need a measure of strength that is ________ , __________ , and
______________ .
objective
numeric
not fooled by scales of information
What is the symbol for correlation coefficient?
r
What is the correlation coefficient?
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
TRUE
In order for their to be a perfect negative relationship (in a Q --> Q case )what needs to be the
case?
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?
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?
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?
points will be more spread out on the positive slope
What does it mean when r = 0?
there is no linear relationship
What does it mean when r > -1, but < 0?
intermediate negative relationship
What does it mean when r > 0 but < 1?
intermediate positive relationship
What does it mean when r = 1?
perfect positive relationship
What does it mean when r = -1?
perfect negative relationship
Which numbers will the value of r always fall between?
1 & -1
What are the properties of r?
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
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
c) sing of r denotes direction of relationship
T or F: r ONLY works for quantitative variables
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
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
d) r is a complete summary of 2-variable data
What adds a measure of strength of the relationship in a Q-->Q relationship?
r - correlation coefficient
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
a) resp = stat grade
expl. = ACT math
What is the visual display tool for a Q --> Q case?
scatterplot
What are the numerical study tools for a Q --> Q case?
correlation, regression line
What are the goals for a Q --> Q case?
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
b) 20
What are the 3 ways to assess a scatterplot?
direction
form
strength
,What are the 3 classes or ways you can categorize the form of a given scatterplot?
linear
nonlinear
non-distinguishable
What is considered an outlier?
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?
FALSE
T or F: a Q --> Q relationship only works for linear relationships?
TRUE
In a linear relationship you need a measure of strength that is ________ , __________ , and
______________ .
objective
numeric
not fooled by scales of information
What is the symbol for correlation coefficient?
r
What is the correlation coefficient?
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
TRUE
In order for their to be a perfect negative relationship (in a Q --> Q case )what needs to be the
case?
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?
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?
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?
points will be more spread out on the positive slope
What does it mean when r = 0?
there is no linear relationship
What does it mean when r > -1, but < 0?
intermediate negative relationship
What does it mean when r > 0 but < 1?
intermediate positive relationship
What does it mean when r = 1?
perfect positive relationship
What does it mean when r = -1?
perfect negative relationship
Which numbers will the value of r always fall between?
1 & -1
What are the properties of r?
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
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
c) sing of r denotes direction of relationship
T or F: r ONLY works for quantitative variables
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
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
d) r is a complete summary of 2-variable data
What adds a measure of strength of the relationship in a Q-->Q relationship?
r - correlation coefficient
