WGU C955 Applied Probability and Statistics
OA 2026/2027 Study Guide | Verified
Questions & Answers with Detailed
Solutions | Objective Assessment Exam Prep
WGU C955 APPLIED PROBABILITY AND STATISTICS | OA STUDY GUIDE
====================================================================
==========
• This study guide provides 200 comprehensive practice questions covering all
major topics on the WGU C955 Objective Assessment exam with verified answers
and detailed solutions.
• Use this material to reinforce conceptual understanding, identify knowledge gaps,
and build confidence in probability, statistics, hypothesis testing, and data analysis
before taking your official exam.
====================================================================
==========
1. A data set contains the values: 3, 5, 7, 9, 11. What is the mean of this data
set?
A) 5
B) 7
C) 8
D) 9
E) 10
✓ CORRECT ANSWER: B) 7
RATIONALE: The mean is calculated by summing all values and dividing by the
number of observations. (3+5+7+9+11)/5 = 35/5 = 7. This represents the arithmetic
average and is a measure of central tendency commonly used in descriptive
statistics.
2. Which of the following is the middle value in an ordered data set?
,A) Mean
B) Mode
C) Median
D) Range
E) Standard deviation
✓ CORRECT ANSWER: C) Median
RATIONALE: The median is the value that divides the data into two equal halves
when arranged in order. It is particularly useful for data sets with outliers since it is
not affected by extreme values, unlike the mean. In a data set with an even number
of observations, the median is the average of the two middle values.
3. A data set has a mean of 50 and a standard deviation of 10. What does a
standard deviation of 10 indicate?
A) The average value is 50
B) The data varies by an average of 10 units from the mean
C) All values are within 10 units of 50
D) The range of data is 10
E) The median is 40
✓ CORRECT ANSWER: B) The data varies by an average of 10 units from the
mean
RATIONALE: Standard deviation measures the average distance of each data point
from the mean. A standard deviation of 10 means that, on average, the data points
deviate 10 units from the mean of 50. This is a measure of dispersion or variability
in the data set.
4. What is the probability of rolling a fair six-sided die and getting a 4?
,A) 1/6
B) 1/4
C) 1/3
D) 1/2
E) 2/3
✓ CORRECT ANSWER: A) 1/6
RATIONALE: A fair six-sided die has six equally likely outcomes (1, 2, 3, 4, 5, 6). The
probability of any single outcome is 1 divided by the total number of possible
outcomes, which is 1/6. This demonstrates the basic principle of classical
probability for equally likely events.
5. If two fair coins are flipped simultaneously, what is the probability of
getting at least one heads?
A) 1/4
B) 1/3
C) 1/2
D) 3/4
E) 1
✓ CORRECT ANSWER: D) 3/4
RATIONALE: The possible outcomes are HH, HT, TH, TT (4 equally likely outcomes).
Three of these outcomes contain at least one heads: HH, HT, and TH. Therefore, the
probability is 3/4. Alternatively, P(at least one H) = 1 - P(no H) = 1 - 1/4 = 3/4.
6. Two events A and B are mutually exclusive. If P(A) = 0.3 and P(B) = 0.2, what
is P(A or B)?
A) 0.06
, B) 0.5
C) 0.6
D) 0.05
E) 0.15
✓ CORRECT ANSWER: B) 0.5
RATIONALE: For mutually exclusive events, P(A or B) = P(A) + P(B) because the
events cannot occur simultaneously. Therefore, P(A or B) = 0.3 + 0.2 = 0.5. The
addition rule applies directly when events are mutually exclusive.
7. If P(A) = 0.4 and P(B|A) = 0.5, what is P(A and B)?
A) 0.9
B) 0.2
C) 0.45
D) 0.1
E) 0.5
✓ CORRECT ANSWER: B) 0.2
RATIONALE: The multiplication rule for conditional probability states that P(A and B)
= P(A) × P(B|A). Substituting the given values: P(A and B) = 0.4 × 0.5 = 0.2. This
represents the probability that both A and B occur.
8. What is Bayes' Theorem used for?
A) Calculating the mean of a distribution
B) Updating probability estimates based on new evidence
C) Determining the mode of a data set
D) Calculating confidence intervals
OA 2026/2027 Study Guide | Verified
Questions & Answers with Detailed
Solutions | Objective Assessment Exam Prep
WGU C955 APPLIED PROBABILITY AND STATISTICS | OA STUDY GUIDE
====================================================================
==========
• This study guide provides 200 comprehensive practice questions covering all
major topics on the WGU C955 Objective Assessment exam with verified answers
and detailed solutions.
• Use this material to reinforce conceptual understanding, identify knowledge gaps,
and build confidence in probability, statistics, hypothesis testing, and data analysis
before taking your official exam.
====================================================================
==========
1. A data set contains the values: 3, 5, 7, 9, 11. What is the mean of this data
set?
A) 5
B) 7
C) 8
D) 9
E) 10
✓ CORRECT ANSWER: B) 7
RATIONALE: The mean is calculated by summing all values and dividing by the
number of observations. (3+5+7+9+11)/5 = 35/5 = 7. This represents the arithmetic
average and is a measure of central tendency commonly used in descriptive
statistics.
2. Which of the following is the middle value in an ordered data set?
,A) Mean
B) Mode
C) Median
D) Range
E) Standard deviation
✓ CORRECT ANSWER: C) Median
RATIONALE: The median is the value that divides the data into two equal halves
when arranged in order. It is particularly useful for data sets with outliers since it is
not affected by extreme values, unlike the mean. In a data set with an even number
of observations, the median is the average of the two middle values.
3. A data set has a mean of 50 and a standard deviation of 10. What does a
standard deviation of 10 indicate?
A) The average value is 50
B) The data varies by an average of 10 units from the mean
C) All values are within 10 units of 50
D) The range of data is 10
E) The median is 40
✓ CORRECT ANSWER: B) The data varies by an average of 10 units from the
mean
RATIONALE: Standard deviation measures the average distance of each data point
from the mean. A standard deviation of 10 means that, on average, the data points
deviate 10 units from the mean of 50. This is a measure of dispersion or variability
in the data set.
4. What is the probability of rolling a fair six-sided die and getting a 4?
,A) 1/6
B) 1/4
C) 1/3
D) 1/2
E) 2/3
✓ CORRECT ANSWER: A) 1/6
RATIONALE: A fair six-sided die has six equally likely outcomes (1, 2, 3, 4, 5, 6). The
probability of any single outcome is 1 divided by the total number of possible
outcomes, which is 1/6. This demonstrates the basic principle of classical
probability for equally likely events.
5. If two fair coins are flipped simultaneously, what is the probability of
getting at least one heads?
A) 1/4
B) 1/3
C) 1/2
D) 3/4
E) 1
✓ CORRECT ANSWER: D) 3/4
RATIONALE: The possible outcomes are HH, HT, TH, TT (4 equally likely outcomes).
Three of these outcomes contain at least one heads: HH, HT, and TH. Therefore, the
probability is 3/4. Alternatively, P(at least one H) = 1 - P(no H) = 1 - 1/4 = 3/4.
6. Two events A and B are mutually exclusive. If P(A) = 0.3 and P(B) = 0.2, what
is P(A or B)?
A) 0.06
, B) 0.5
C) 0.6
D) 0.05
E) 0.15
✓ CORRECT ANSWER: B) 0.5
RATIONALE: For mutually exclusive events, P(A or B) = P(A) + P(B) because the
events cannot occur simultaneously. Therefore, P(A or B) = 0.3 + 0.2 = 0.5. The
addition rule applies directly when events are mutually exclusive.
7. If P(A) = 0.4 and P(B|A) = 0.5, what is P(A and B)?
A) 0.9
B) 0.2
C) 0.45
D) 0.1
E) 0.5
✓ CORRECT ANSWER: B) 0.2
RATIONALE: The multiplication rule for conditional probability states that P(A and B)
= P(A) × P(B|A). Substituting the given values: P(A and B) = 0.4 × 0.5 = 0.2. This
represents the probability that both A and B occur.
8. What is Bayes' Theorem used for?
A) Calculating the mean of a distribution
B) Updating probability estimates based on new evidence
C) Determining the mode of a data set
D) Calculating confidence intervals
