WGU COURSE CONTENT
WGU C955 Probability and Statistics Objective Assessment Exam
(2026/2027) with Questions and Revised Answers, 100% Guarantee Pass
(Updated) 2026/2027
A+
Complete Domain Coverage
A+ 5 100%
QUESTIONS VERIFIED CORE DOMAINS COVERED RATIONALES INCLUDED
CATEGORIES
Descriptive Statistics and Data Displays (Q1-Q14)
Probability Concepts and Rules (Q15-Q28)
Discrete and Continuous Probability Distributions (Q29-Q42)
Sampling, Estimation, and Confidence Intervals (Q43-Q56)
Hypothesis Testing, Correlation, and Regression (Q57-Q70)
STUVIAACTUALEXAM
,EXAM INTRODUCTION
This examination assesses knowledge and application of probability and statistics concepts including descriptive
methods, probability rules, distributions, sampling and estimation, and hypothesis testing with correlation and regression.
Each question is worth one mark. A minimum score of 75 percent is required to pass. Select the single best answer.
SECTION 1: DESCRIPTIVE STATISTICS AND DATA DISPLAYS
Q1
A quality analyst records the number of defects found in 20 consecutive batches of electronic components. The values
are 2, 0, 1, 3, 1, 0, 2, 4, 1, 2, 0, 1, 3, 2, 1, 0, 2, 1, 3, 2. The analyst needs a single measure that represents the center
of this distribution. Which measure is least affected by the single high value of 4?
A. The arithmetic mean of all 20 observations
B. The median of the ordered data set
C. The range calculated as maximum minus minimum
D. The sum of all observations divided by the sample size
Correct Answer: B
Rationale:
The median is resistant to extreme values. The mean and the sum divided by n are the same measure and are pulled upward by the
value 4; the range is a measure of spread, not center.
Q2
A researcher collects resting heart rates for 15 adults and constructs a stem-and-leaf plot. The plot shows most values
clustered between 60 and 75 with one leaf of 98. How should the researcher describe the shape of the distribution?
A. Symmetric and bell-shaped with no unusual observations
B. Right-skewed because of a high outlier relative to the main cluster
C. Left-skewed because most data are at the high end of the scale
D. Uniform because every heart-rate value appears equally often
Correct Answer: B
Rationale:
A single high value (98) extending far above a cluster of lower values produces a right (positive) skew. Symmetric or left-skewed
descriptions do not match this pattern.
Q3
An instructor calculates the sample standard deviation of exam scores and obtains s = 12.4. The instructor wants a
measure of spread that is in the original units of the data and is not squared. Which statement correctly interprets this
value?
A. The variance of the scores is 12.4 points
B. A typical score deviates about 12.4 points from the sample mean
C. Every score is exactly 12.4 points away from the mean
D. The interquartile range of the scores is 12.4 points
Correct Answer: B
Rationale:
The sample standard deviation measures typical distance from the mean in the original units. Variance is the square of s; IQR is a
different resistant measure of spread.
WGU C955 Probability and Statistics - 2026/2027 Page 2
, Q4
A data set of 40 household incomes is strongly right-skewed because of a few very high values. The analyst wants a
measure of center that is appropriate for reporting a typical income. Which measure should the analyst prefer?
A. The arithmetic mean because it uses every data value
B. The median because it is not pulled by extreme high incomes
C. The mode because income is a continuous variable
D. The midrange because it averages the minimum and maximum
Correct Answer: B
Rationale:
For right-skewed income data the median better represents a typical value. The mean is inflated by extreme high incomes; the mode
is less useful for continuous data; the midrange is highly sensitive to extremes.
Q5
A frequency histogram of commute times (in minutes) has bars of height 5, 12, 18, 9, and 4 for the classes 0-10, 10-20,
20-30, 30-40, and 40-50. What is the relative frequency of the 20-30 minute class?
A. 18 percent
B. Approximately 37.5 percent
C. 9/48 or 18.75 percent
D. The absolute frequency 18 cannot be converted to relative frequency
Correct Answer: B
Rationale:
Total frequency is 5+12+18+9+4 = 48. Relative frequency of the 20-30 class is 18/48 = 0.375 or 37.5 percent.
Q6
A boxplot of annual rainfall amounts for 25 cities shows a box from 28 to 42 inches, a median line at 35, a lower
whisker to 18, and an upper whisker to 55 with one point plotted at 72. How should the point at 72 be interpreted?
A. It is the maximum value and lies within the upper whisker
B. It is an outlier that falls beyond the upper fence of the boxplot
C. It represents the third quartile of the rainfall distribution
D. It indicates that the distribution is left-skewed
Correct Answer: B
Rationale:
Points plotted individually beyond the whiskers are outliers. The whisker ends at 55, so 72 is beyond the upper fence.
Q7
A sample of 8 exam scores has mean 78 and standard deviation 6. Each score is increased by 5 points because of a
curve. What happens to the mean and standard deviation after the curve?
A. The mean becomes 83 and the standard deviation remains 6
B. The mean remains 78 and the standard deviation becomes 11
C. Both the mean and standard deviation increase by 5
D. The mean becomes 83 and the standard deviation becomes 11
Correct Answer: A
Rationale:
Adding a constant to every value shifts the mean by that constant but does not change the spread, so the standard deviation is
unchanged.
WGU C955 Probability and Statistics - 2026/2027 Page 3
WGU C955 Probability and Statistics Objective Assessment Exam
(2026/2027) with Questions and Revised Answers, 100% Guarantee Pass
(Updated) 2026/2027
A+
Complete Domain Coverage
A+ 5 100%
QUESTIONS VERIFIED CORE DOMAINS COVERED RATIONALES INCLUDED
CATEGORIES
Descriptive Statistics and Data Displays (Q1-Q14)
Probability Concepts and Rules (Q15-Q28)
Discrete and Continuous Probability Distributions (Q29-Q42)
Sampling, Estimation, and Confidence Intervals (Q43-Q56)
Hypothesis Testing, Correlation, and Regression (Q57-Q70)
STUVIAACTUALEXAM
,EXAM INTRODUCTION
This examination assesses knowledge and application of probability and statistics concepts including descriptive
methods, probability rules, distributions, sampling and estimation, and hypothesis testing with correlation and regression.
Each question is worth one mark. A minimum score of 75 percent is required to pass. Select the single best answer.
SECTION 1: DESCRIPTIVE STATISTICS AND DATA DISPLAYS
Q1
A quality analyst records the number of defects found in 20 consecutive batches of electronic components. The values
are 2, 0, 1, 3, 1, 0, 2, 4, 1, 2, 0, 1, 3, 2, 1, 0, 2, 1, 3, 2. The analyst needs a single measure that represents the center
of this distribution. Which measure is least affected by the single high value of 4?
A. The arithmetic mean of all 20 observations
B. The median of the ordered data set
C. The range calculated as maximum minus minimum
D. The sum of all observations divided by the sample size
Correct Answer: B
Rationale:
The median is resistant to extreme values. The mean and the sum divided by n are the same measure and are pulled upward by the
value 4; the range is a measure of spread, not center.
Q2
A researcher collects resting heart rates for 15 adults and constructs a stem-and-leaf plot. The plot shows most values
clustered between 60 and 75 with one leaf of 98. How should the researcher describe the shape of the distribution?
A. Symmetric and bell-shaped with no unusual observations
B. Right-skewed because of a high outlier relative to the main cluster
C. Left-skewed because most data are at the high end of the scale
D. Uniform because every heart-rate value appears equally often
Correct Answer: B
Rationale:
A single high value (98) extending far above a cluster of lower values produces a right (positive) skew. Symmetric or left-skewed
descriptions do not match this pattern.
Q3
An instructor calculates the sample standard deviation of exam scores and obtains s = 12.4. The instructor wants a
measure of spread that is in the original units of the data and is not squared. Which statement correctly interprets this
value?
A. The variance of the scores is 12.4 points
B. A typical score deviates about 12.4 points from the sample mean
C. Every score is exactly 12.4 points away from the mean
D. The interquartile range of the scores is 12.4 points
Correct Answer: B
Rationale:
The sample standard deviation measures typical distance from the mean in the original units. Variance is the square of s; IQR is a
different resistant measure of spread.
WGU C955 Probability and Statistics - 2026/2027 Page 2
, Q4
A data set of 40 household incomes is strongly right-skewed because of a few very high values. The analyst wants a
measure of center that is appropriate for reporting a typical income. Which measure should the analyst prefer?
A. The arithmetic mean because it uses every data value
B. The median because it is not pulled by extreme high incomes
C. The mode because income is a continuous variable
D. The midrange because it averages the minimum and maximum
Correct Answer: B
Rationale:
For right-skewed income data the median better represents a typical value. The mean is inflated by extreme high incomes; the mode
is less useful for continuous data; the midrange is highly sensitive to extremes.
Q5
A frequency histogram of commute times (in minutes) has bars of height 5, 12, 18, 9, and 4 for the classes 0-10, 10-20,
20-30, 30-40, and 40-50. What is the relative frequency of the 20-30 minute class?
A. 18 percent
B. Approximately 37.5 percent
C. 9/48 or 18.75 percent
D. The absolute frequency 18 cannot be converted to relative frequency
Correct Answer: B
Rationale:
Total frequency is 5+12+18+9+4 = 48. Relative frequency of the 20-30 class is 18/48 = 0.375 or 37.5 percent.
Q6
A boxplot of annual rainfall amounts for 25 cities shows a box from 28 to 42 inches, a median line at 35, a lower
whisker to 18, and an upper whisker to 55 with one point plotted at 72. How should the point at 72 be interpreted?
A. It is the maximum value and lies within the upper whisker
B. It is an outlier that falls beyond the upper fence of the boxplot
C. It represents the third quartile of the rainfall distribution
D. It indicates that the distribution is left-skewed
Correct Answer: B
Rationale:
Points plotted individually beyond the whiskers are outliers. The whisker ends at 55, so 72 is beyond the upper fence.
Q7
A sample of 8 exam scores has mean 78 and standard deviation 6. Each score is increased by 5 points because of a
curve. What happens to the mean and standard deviation after the curve?
A. The mean becomes 83 and the standard deviation remains 6
B. The mean remains 78 and the standard deviation becomes 11
C. Both the mean and standard deviation increase by 5
D. The mean becomes 83 and the standard deviation becomes 11
Correct Answer: A
Rationale:
Adding a constant to every value shifts the mean by that constant but does not change the spread, so the standard deviation is
unchanged.
WGU C955 Probability and Statistics - 2026/2027 Page 3
