WGU C784 Applied Healthcare Statistics Objective
Assessment – WGU C784 Study Guide, Original
Practice Questions & Answers, Objective Assessment
Preparation, Comprehensive Applied Healthcare
Statistics Review, Probability, Descriptive Statistics,
Algebra, Regression, Correlation, Data
Interpretation & Healthcare Statistics
Question 1: A clinical trial is studying the effectiveness of a new drug on
lowering systolic blood pressure. The researchers measure each participant's
blood pressure before and after the 12-week treatment period. Which of the
following measures would be most appropriate for the researchers to use to
determine if the average change in blood pressure is statistically significant?
A. One-sample z-test
B. Paired t-test
C. Two-sample t-test (independent)
D. Chi-square test of independence
CORRECT ANSWER: B. Paired t-test
Rationale: Because the same participants are measured twice (before and after
treatment), the data are paired. The paired t-test is used to compare the means of two
related groups to determine if there is a statistically significant difference between these
means. A one-sample z-test is for comparing a sample mean to a known population
mean. An independent t-test is for comparing two separate groups. A Chi-square test is
for categorical data.
Question 2: A histogram of patient wait times in an emergency room is heavily
skewed to the right. Which measure of central tendency would be most
appropriate to report for this data?
A. Mean
B. Median
C. Mode
D. Range
CORRECT ANSWER: B. Median
Rationale: In a right-skewed distribution, the mean is pulled in the direction of the tail
(towards higher values) and is not representative of the "typical" value. The median is
resistant to outliers and skewness, making it the best measure of central tendency for
skewed data. The mode is the most frequent value, and the range is a measure of
spread, not central tendency.
,Question 3: A researcher wants to estimate the mean fasting blood glucose
level of all adults in a city with 95% confidence. They collect a random sample
of 100 adults and find a sample mean of 95 mg/dL and a sample standard
deviation of 15 mg/dL. Which distribution should be used to construct the
confidence interval?
A. Standard normal (Z) distribution
B. t-distribution with 99 degrees of freedom
C. t-distribution with 100 degrees of freedom
D. Chi-square distribution
CORRECT ANSWER: B. t-distribution with 99 degrees of freedom
Rationale: Since the population standard deviation is unknown and the sample size is
100 (n < 30 is a common guideline, but when sigma is unknown, the t-distribution is
always the correct choice for means), the t-distribution should be used. The degrees of
freedom are n-1, which is 100 - 1 = 99. The Z-distribution is used when the population
standard deviation is known or the sample size is very large and sigma is known.
Question 4: In a study, the incidence of hospital-acquired infections was
compared between two different wards. The researchers found a relative risk
(RR) of 2.5. How should this result be interpreted?
A. The infection rate is 2.5 times higher in the first ward compared to the second ward.
B. The infection rate is 2.5% higher in the first ward compared to the second ward.
C. The infection rate is 2.5 times lower in the first ward compared to the second ward.
D. There is a 2.5% absolute increase in infection risk.
CORRECT ANSWER: A. The infection rate is 2.5 times higher in the first ward
compared to the second ward.
Rationale: Relative risk (RR) is the ratio of the probability of an event occurring in the
exposed group versus a non-exposed group. An RR of 2.5 means that the risk (or rate) in
the first ward is 2.5 times the risk in the second ward. It does not represent a percentage
point difference (which would be absolute risk difference).
Question 5: A nurse is calculating the body mass index (BMI) for a patient who
weighs 180 pounds and is 5 feet 6 inches tall. What is the patient's BMI? (Use
the formula: BMI = 703 * weight (lbs) / height (in)^2)
A. 25.0
B. 29.0
C. 32.7
D. 35.2
CORRECT ANSWER: B. 29.0
,Rationale: First, convert height to inches: 5 feet = 60 inches, plus 6 inches = 66 inches.
Then, BMI = 703 * 180 / (66^2) = 703 * = 126,,356 = 29.05. This
rounds to 29.0. A BMI of 29.0 is in the overweight category.
Question 6: A clinical study reports that the difference in mean pain scores
between a treatment and placebo group is -2.3 with a 95% confidence interval
of (-3.5, -1.1). What is the correct interpretation of this interval?
A. There is no statistically significant difference because the interval does not contain 0.
B. The true population mean difference is likely between -3.5 and -1.1, and the
treatment is effective.
C. The placebo is significantly better than the treatment.
D. The results are not statistically significant because the interval is negative.
CORRECT ANSWER: B. The true population mean difference is likely between -
3.5 and -1.1, and the treatment is effective.
Rationale: A 95% confidence interval provides a range of plausible values for the true
population parameter. Since the interval does not contain zero and is entirely negative
(meaning the treatment group has a lower pain score), the treatment is considered
statistically significantly better than the placebo. The negative interval indicates the
treatment reduces pain.
Question 7: Which of the following correlation coefficients indicates the
strongest linear relationship between two variables?
A. r = -0.90
B. r = 0.85
C. r = -0.50
D. r = 0.10
CORRECT ANSWER: A. r = -0.90
Rationale: The strength of a linear relationship is determined by the absolute value of
the correlation coefficient. The closer |r| is to 1, the stronger the linear relationship. |-
0.90| = 0.90, which is greater than 0.85, 0.50, and 0.10. The sign indicates the direction
(positive or negative), but strength is based on the magnitude.
Question 8: A quality improvement team is using a p-chart to monitor the
proportion of incorrect medication administrations. This type of chart is used
for what kind of data?
A. Continuous numerical data
B. Categorical or count data
, C. Time-to-event data
D. Ranked data
CORRECT ANSWER: B. Categorical or count data
Rationale: A p-chart is a type of control chart used for monitoring the proportion of
defective items or events in a process. It is specifically designed for attribute data, which
is categorical (e.g., pass/fail, yes/no, correct/incorrect). For continuous numerical data
(like weight or temperature), an X-bar or R-chart would be used.
Question 9: A researcher wants to test if there is an association between
smoking status (smoker/non-smoker) and the development of lung cancer
(yes/no). What is the most appropriate statistical test?
A. Independent t-test
B. Paired t-test
C. Chi-square test of independence
D. Pearson correlation
CORRECT ANSWER: C. Chi-square test of independence
Rationale: Both smoking status and lung cancer development are categorical variables.
The Chi-square test of independence is used to determine if there is a significant
association between two categorical variables. T-tests are for comparing means, and
Pearson correlation is for assessing the linear relationship between two continuous
variables.
Question 10: A medication's half-life is defined as the time it takes for the
concentration of the drug in the body to reduce to half its initial value. If a
drug has a half-life of 6 hours, what percentage of the original dose remains in
the body after 24 hours?
A. 50%
B. 25%
C. 12.5%
D. 6.25%
CORRECT ANSWER: D. 6.25%
Rationale: After 24 hours, which is 4 half-lives ( = 4), the remaining amount is
(1/2)^4 = 1/16 = 6.25%. After 1 half-life: 50%; 2: 25%; 3: 12.5%; 4: 6.25%.
Question 11: A study collects data on patient ages. The ages are: 22, 25, 28, 32,
35, 35, 40, 45, 50, 58. What is the interquartile range (IQR) of this dataset?
Assessment – WGU C784 Study Guide, Original
Practice Questions & Answers, Objective Assessment
Preparation, Comprehensive Applied Healthcare
Statistics Review, Probability, Descriptive Statistics,
Algebra, Regression, Correlation, Data
Interpretation & Healthcare Statistics
Question 1: A clinical trial is studying the effectiveness of a new drug on
lowering systolic blood pressure. The researchers measure each participant's
blood pressure before and after the 12-week treatment period. Which of the
following measures would be most appropriate for the researchers to use to
determine if the average change in blood pressure is statistically significant?
A. One-sample z-test
B. Paired t-test
C. Two-sample t-test (independent)
D. Chi-square test of independence
CORRECT ANSWER: B. Paired t-test
Rationale: Because the same participants are measured twice (before and after
treatment), the data are paired. The paired t-test is used to compare the means of two
related groups to determine if there is a statistically significant difference between these
means. A one-sample z-test is for comparing a sample mean to a known population
mean. An independent t-test is for comparing two separate groups. A Chi-square test is
for categorical data.
Question 2: A histogram of patient wait times in an emergency room is heavily
skewed to the right. Which measure of central tendency would be most
appropriate to report for this data?
A. Mean
B. Median
C. Mode
D. Range
CORRECT ANSWER: B. Median
Rationale: In a right-skewed distribution, the mean is pulled in the direction of the tail
(towards higher values) and is not representative of the "typical" value. The median is
resistant to outliers and skewness, making it the best measure of central tendency for
skewed data. The mode is the most frequent value, and the range is a measure of
spread, not central tendency.
,Question 3: A researcher wants to estimate the mean fasting blood glucose
level of all adults in a city with 95% confidence. They collect a random sample
of 100 adults and find a sample mean of 95 mg/dL and a sample standard
deviation of 15 mg/dL. Which distribution should be used to construct the
confidence interval?
A. Standard normal (Z) distribution
B. t-distribution with 99 degrees of freedom
C. t-distribution with 100 degrees of freedom
D. Chi-square distribution
CORRECT ANSWER: B. t-distribution with 99 degrees of freedom
Rationale: Since the population standard deviation is unknown and the sample size is
100 (n < 30 is a common guideline, but when sigma is unknown, the t-distribution is
always the correct choice for means), the t-distribution should be used. The degrees of
freedom are n-1, which is 100 - 1 = 99. The Z-distribution is used when the population
standard deviation is known or the sample size is very large and sigma is known.
Question 4: In a study, the incidence of hospital-acquired infections was
compared between two different wards. The researchers found a relative risk
(RR) of 2.5. How should this result be interpreted?
A. The infection rate is 2.5 times higher in the first ward compared to the second ward.
B. The infection rate is 2.5% higher in the first ward compared to the second ward.
C. The infection rate is 2.5 times lower in the first ward compared to the second ward.
D. There is a 2.5% absolute increase in infection risk.
CORRECT ANSWER: A. The infection rate is 2.5 times higher in the first ward
compared to the second ward.
Rationale: Relative risk (RR) is the ratio of the probability of an event occurring in the
exposed group versus a non-exposed group. An RR of 2.5 means that the risk (or rate) in
the first ward is 2.5 times the risk in the second ward. It does not represent a percentage
point difference (which would be absolute risk difference).
Question 5: A nurse is calculating the body mass index (BMI) for a patient who
weighs 180 pounds and is 5 feet 6 inches tall. What is the patient's BMI? (Use
the formula: BMI = 703 * weight (lbs) / height (in)^2)
A. 25.0
B. 29.0
C. 32.7
D. 35.2
CORRECT ANSWER: B. 29.0
,Rationale: First, convert height to inches: 5 feet = 60 inches, plus 6 inches = 66 inches.
Then, BMI = 703 * 180 / (66^2) = 703 * = 126,,356 = 29.05. This
rounds to 29.0. A BMI of 29.0 is in the overweight category.
Question 6: A clinical study reports that the difference in mean pain scores
between a treatment and placebo group is -2.3 with a 95% confidence interval
of (-3.5, -1.1). What is the correct interpretation of this interval?
A. There is no statistically significant difference because the interval does not contain 0.
B. The true population mean difference is likely between -3.5 and -1.1, and the
treatment is effective.
C. The placebo is significantly better than the treatment.
D. The results are not statistically significant because the interval is negative.
CORRECT ANSWER: B. The true population mean difference is likely between -
3.5 and -1.1, and the treatment is effective.
Rationale: A 95% confidence interval provides a range of plausible values for the true
population parameter. Since the interval does not contain zero and is entirely negative
(meaning the treatment group has a lower pain score), the treatment is considered
statistically significantly better than the placebo. The negative interval indicates the
treatment reduces pain.
Question 7: Which of the following correlation coefficients indicates the
strongest linear relationship between two variables?
A. r = -0.90
B. r = 0.85
C. r = -0.50
D. r = 0.10
CORRECT ANSWER: A. r = -0.90
Rationale: The strength of a linear relationship is determined by the absolute value of
the correlation coefficient. The closer |r| is to 1, the stronger the linear relationship. |-
0.90| = 0.90, which is greater than 0.85, 0.50, and 0.10. The sign indicates the direction
(positive or negative), but strength is based on the magnitude.
Question 8: A quality improvement team is using a p-chart to monitor the
proportion of incorrect medication administrations. This type of chart is used
for what kind of data?
A. Continuous numerical data
B. Categorical or count data
, C. Time-to-event data
D. Ranked data
CORRECT ANSWER: B. Categorical or count data
Rationale: A p-chart is a type of control chart used for monitoring the proportion of
defective items or events in a process. It is specifically designed for attribute data, which
is categorical (e.g., pass/fail, yes/no, correct/incorrect). For continuous numerical data
(like weight or temperature), an X-bar or R-chart would be used.
Question 9: A researcher wants to test if there is an association between
smoking status (smoker/non-smoker) and the development of lung cancer
(yes/no). What is the most appropriate statistical test?
A. Independent t-test
B. Paired t-test
C. Chi-square test of independence
D. Pearson correlation
CORRECT ANSWER: C. Chi-square test of independence
Rationale: Both smoking status and lung cancer development are categorical variables.
The Chi-square test of independence is used to determine if there is a significant
association between two categorical variables. T-tests are for comparing means, and
Pearson correlation is for assessing the linear relationship between two continuous
variables.
Question 10: A medication's half-life is defined as the time it takes for the
concentration of the drug in the body to reduce to half its initial value. If a
drug has a half-life of 6 hours, what percentage of the original dose remains in
the body after 24 hours?
A. 50%
B. 25%
C. 12.5%
D. 6.25%
CORRECT ANSWER: D. 6.25%
Rationale: After 24 hours, which is 4 half-lives ( = 4), the remaining amount is
(1/2)^4 = 1/16 = 6.25%. After 1 half-life: 50%; 2: 25%; 3: 12.5%; 4: 6.25%.
Question 11: A study collects data on patient ages. The ages are: 22, 25, 28, 32,
35, 35, 40, 45, 50, 58. What is the interquartile range (IQR) of this dataset?
