STRAIGHTERLINE INTRODUCTION TO
STATISTICS EXAM QUESTIONS AND
ANSWERS
Visual display and numerical summary for C->C - Answer-Two way table and
conditional percentages
Visual display and numerical summary for C->Q - Answer-Side by side box plots and
descriptive statistics
Visual display and numerical summary for Q->Q - Answer-Scatterplot and correlation
coefficient (r)
Standard Deviation Rule - Answer-Approximately
68% of observations fall within 1 sd of the mean,
95% within 2 sd,
99.7% (or virtually all) within 3 sds
Interquartile Range (IQR) - Answer-Middle 50% of the data
IQR= Q3-Q1
Finding an outlier using IQR - Answer-An observation is considered a suspected outlier
if it is:
less than Q1 - 1.5(IQR), or
more than Q3 + 1.5(IQR).
Interpreting scatterplots:
1. positive relationship displays as
2. negative relationship displays as - Answer-1. upward slope
2. downward slope
Interpreting Scatterplots:
How to tell if a linear relationship is strong or weak - Answer-closer to -1 is a strong
negative linear relationship
closer to +1 is a strong positive linear relationship
close to 0 is a weak linear relationship
Interpreting Scatterplots:
Linear regression - Answer-Finding the line that best fits the pattern of the linear
relationship (the line that describes how the response variable linearly depends on the
explanatory variable
Interpreting Scatterplots:
, Least Squares Regression Line - Answer-Has the smallest sum of squared vertical
deviations of the data points from the line.
Interpreting Scatterplots:
Extrapolation - Answer-Prediction for ranges of the explanatory variable that are not in
the data; is not reliable and should be avoided
Association (does/does not) imply causation. - Answer-Does not
Lurking Variable - Answer-a variable that is not among the explanatory or response
variables in a study, but could substantially affect your interpretation of the relationship
among those variables
Simpson's paradox - Answer-When a lurking variable causes you to rethink the direction
of an association
Probability sampling plan - Answer-any sampling plan that relies on random selection
(avoids bias).
Simple Random Sampling - Answer-Every member of the population has an equal
probability of being selected for the sample
Cluster Sampling - Answer-Used when the population is naturally divided into groups.
Take a random sample of clusters and use all individuals within those clusters as the
sample.
Stratified sampling - Answer-Used when the population is naturally divided into sub-
populations called stratum. Choose a simple random sample from each stratum and use
these together as the sample.
Multistage sampling - Answer-a probability sampling technique involving at least two
stages: a random sample of clusters followed by a random sample of people within the
selected clusters
Observational study - Answer-values of the variable or variables of interest are recorded
as they naturally occur; no interference
Sample surveys - Answer-a particular type of observational study in which individuals
report variables' values themselves, frequently by giving their opinions.
Experiment - Answer-researchers "take control" of the values of the explanatory
variable because they want to see how changes in the value of the explanatory variable
affect the response variable
The Complement Rule - Answer-P(not A) = 1 - P(A)
useful for finding events of the type "at least one of..."
STATISTICS EXAM QUESTIONS AND
ANSWERS
Visual display and numerical summary for C->C - Answer-Two way table and
conditional percentages
Visual display and numerical summary for C->Q - Answer-Side by side box plots and
descriptive statistics
Visual display and numerical summary for Q->Q - Answer-Scatterplot and correlation
coefficient (r)
Standard Deviation Rule - Answer-Approximately
68% of observations fall within 1 sd of the mean,
95% within 2 sd,
99.7% (or virtually all) within 3 sds
Interquartile Range (IQR) - Answer-Middle 50% of the data
IQR= Q3-Q1
Finding an outlier using IQR - Answer-An observation is considered a suspected outlier
if it is:
less than Q1 - 1.5(IQR), or
more than Q3 + 1.5(IQR).
Interpreting scatterplots:
1. positive relationship displays as
2. negative relationship displays as - Answer-1. upward slope
2. downward slope
Interpreting Scatterplots:
How to tell if a linear relationship is strong or weak - Answer-closer to -1 is a strong
negative linear relationship
closer to +1 is a strong positive linear relationship
close to 0 is a weak linear relationship
Interpreting Scatterplots:
Linear regression - Answer-Finding the line that best fits the pattern of the linear
relationship (the line that describes how the response variable linearly depends on the
explanatory variable
Interpreting Scatterplots:
, Least Squares Regression Line - Answer-Has the smallest sum of squared vertical
deviations of the data points from the line.
Interpreting Scatterplots:
Extrapolation - Answer-Prediction for ranges of the explanatory variable that are not in
the data; is not reliable and should be avoided
Association (does/does not) imply causation. - Answer-Does not
Lurking Variable - Answer-a variable that is not among the explanatory or response
variables in a study, but could substantially affect your interpretation of the relationship
among those variables
Simpson's paradox - Answer-When a lurking variable causes you to rethink the direction
of an association
Probability sampling plan - Answer-any sampling plan that relies on random selection
(avoids bias).
Simple Random Sampling - Answer-Every member of the population has an equal
probability of being selected for the sample
Cluster Sampling - Answer-Used when the population is naturally divided into groups.
Take a random sample of clusters and use all individuals within those clusters as the
sample.
Stratified sampling - Answer-Used when the population is naturally divided into sub-
populations called stratum. Choose a simple random sample from each stratum and use
these together as the sample.
Multistage sampling - Answer-a probability sampling technique involving at least two
stages: a random sample of clusters followed by a random sample of people within the
selected clusters
Observational study - Answer-values of the variable or variables of interest are recorded
as they naturally occur; no interference
Sample surveys - Answer-a particular type of observational study in which individuals
report variables' values themselves, frequently by giving their opinions.
Experiment - Answer-researchers "take control" of the values of the explanatory
variable because they want to see how changes in the value of the explanatory variable
affect the response variable
The Complement Rule - Answer-P(not A) = 1 - P(A)
useful for finding events of the type "at least one of..."
