WGU PROBABILITY AND STATISTICS C955 PRACTICE
EXAMINATION 100 QUESTIONS WITH CORRECT
ANSWERS AND VERIFIED RATIONALES PLUS ANSWER
KEY 2026-2027 Q&A GRADED A+ INSTANT DOWNLOAD
PDF
Question 1
What is the primary difference between a boxplot and a histogram as
visual representations of data?
A) Boxplots show the exact frequency of data points; histograms show
the spread
B) Boxplots are used only for categorical data; histograms for numerical
data
C) Boxplots display the five-number summary and are better for
comparing distributions; histograms show the shape of the frequency
distribution
D) There is no meaningful difference between them
Rationale: A boxplot displays the five-number summary (minimum, Q1,
median, Q3, maximum), making it ideal for comparing multiple
distributions. Histograms show the shape of the data distribution by
grouping data into intervals and displaying frequencies with bars.
Question 2
Which measure of center should be used for skewed data?
,A) Mean
B) Median
C) Mode
D) Range
Rationale: For skewed data, the median is the preferred measure of
center because it is resistant to extreme values. The mean is sensitive to
outliers and can give a misleading representation of central tendency
for skewed distributions.
Question 3
A data set has a mean of 25 and a standard deviation of 2. What
percentage of the data falls between 23 and 25 if the data is normally
distributed?
A) 34.0%
B) 68.0%
C) 95.0%
D) 99.7%
Rationale: According to the Standard Deviation Rule (68-95-99.7 rule),
68% of data falls within one standard deviation of the mean. Since one
standard deviation from 25 is 23 to 27, and 23 to 25 represents half of
that range, 34% of the data falls between 23 and 25.
Question 4
For a normally distributed data set with a mean of 200 and a standard
deviation of 5, between which two values does 95% of the data fall?
A) 180-220
B) 185-225
,C) 190-210
D) 195-235
Rationale: 95% of data falls within two standard deviations of the mean.
2 × 5 = 10, so 200 - 10 = 190 and 200 + 10 = 210.
Question 5
Which measure of spread is most appropriate for skewed data?
A) Standard deviation
B) Interquartile Range (IQR)
C) Range
D) Variance
Rationale: For skewed data, the IQR is preferred because it measures
the spread of the middle 50% of the data and is not affected by outliers.
Standard deviation is sensitive to extreme values and is more
appropriate for symmetric distributions.
Question 6
What does the correlation coefficient (r) measure?
A) The strength and direction of a linear relationship between two
variables
B) The slope of the regression line
C) The percentage of variation explained by the model
D) The significance of the regression coefficient
Rationale: The correlation coefficient r ranges from -1 to 1. It measures
how close the points are to a line (strength) and whether the trend is
uphill (positive) or downhill (negative).
Question 7
, What is the difference between an explanatory variable and a response
variable?
A) Explanatory variables are categorical; response variables are
numerical
B) Explanatory variables are measured; response variables are
manipulated
C) Explanatory variables are the "cause" in a study; response variables
are the "effect"
D) There is no meaningful difference
Rationale: The explanatory variable is what we think is the "cause" or
predictor in a study. The response variable is what we think is the
"effect" or outcome being measured.
Question 8
Which of the following is an example of discrete data?
A) Speed of a car
B) Weight of a dog
C) Adults in a household
D) Time to go to bed
Rationale: Discrete data has distinct values that can be counted and has
unconnected points (like dots). Examples include days of the week or
adults in a household. Continuous data has values within a range, is
measured, and does not have gaps.
Question 9
What is the purpose of a two-way table in descriptive statistics?
EXAMINATION 100 QUESTIONS WITH CORRECT
ANSWERS AND VERIFIED RATIONALES PLUS ANSWER
KEY 2026-2027 Q&A GRADED A+ INSTANT DOWNLOAD
Question 1
What is the primary difference between a boxplot and a histogram as
visual representations of data?
A) Boxplots show the exact frequency of data points; histograms show
the spread
B) Boxplots are used only for categorical data; histograms for numerical
data
C) Boxplots display the five-number summary and are better for
comparing distributions; histograms show the shape of the frequency
distribution
D) There is no meaningful difference between them
Rationale: A boxplot displays the five-number summary (minimum, Q1,
median, Q3, maximum), making it ideal for comparing multiple
distributions. Histograms show the shape of the data distribution by
grouping data into intervals and displaying frequencies with bars.
Question 2
Which measure of center should be used for skewed data?
,A) Mean
B) Median
C) Mode
D) Range
Rationale: For skewed data, the median is the preferred measure of
center because it is resistant to extreme values. The mean is sensitive to
outliers and can give a misleading representation of central tendency
for skewed distributions.
Question 3
A data set has a mean of 25 and a standard deviation of 2. What
percentage of the data falls between 23 and 25 if the data is normally
distributed?
A) 34.0%
B) 68.0%
C) 95.0%
D) 99.7%
Rationale: According to the Standard Deviation Rule (68-95-99.7 rule),
68% of data falls within one standard deviation of the mean. Since one
standard deviation from 25 is 23 to 27, and 23 to 25 represents half of
that range, 34% of the data falls between 23 and 25.
Question 4
For a normally distributed data set with a mean of 200 and a standard
deviation of 5, between which two values does 95% of the data fall?
A) 180-220
B) 185-225
,C) 190-210
D) 195-235
Rationale: 95% of data falls within two standard deviations of the mean.
2 × 5 = 10, so 200 - 10 = 190 and 200 + 10 = 210.
Question 5
Which measure of spread is most appropriate for skewed data?
A) Standard deviation
B) Interquartile Range (IQR)
C) Range
D) Variance
Rationale: For skewed data, the IQR is preferred because it measures
the spread of the middle 50% of the data and is not affected by outliers.
Standard deviation is sensitive to extreme values and is more
appropriate for symmetric distributions.
Question 6
What does the correlation coefficient (r) measure?
A) The strength and direction of a linear relationship between two
variables
B) The slope of the regression line
C) The percentage of variation explained by the model
D) The significance of the regression coefficient
Rationale: The correlation coefficient r ranges from -1 to 1. It measures
how close the points are to a line (strength) and whether the trend is
uphill (positive) or downhill (negative).
Question 7
, What is the difference between an explanatory variable and a response
variable?
A) Explanatory variables are categorical; response variables are
numerical
B) Explanatory variables are measured; response variables are
manipulated
C) Explanatory variables are the "cause" in a study; response variables
are the "effect"
D) There is no meaningful difference
Rationale: The explanatory variable is what we think is the "cause" or
predictor in a study. The response variable is what we think is the
"effect" or outcome being measured.
Question 8
Which of the following is an example of discrete data?
A) Speed of a car
B) Weight of a dog
C) Adults in a household
D) Time to go to bed
Rationale: Discrete data has distinct values that can be counted and has
unconnected points (like dots). Examples include days of the week or
adults in a household. Continuous data has values within a range, is
measured, and does not have gaps.
Question 9
What is the purpose of a two-way table in descriptive statistics?
