Wilkes University NSG 535 Exam 3 (pdf) | 2026/2027 | Advanced
Practice Psych Mental Health I Q&A | Psychiatric Nursing
1. Which statistical concept describes the spread or variance of a set of
measurements about the mean?
A) Coefficient of variation
B) Confidence interval
C) Standard deviation
D) Gaussian distribution
Correct Answer: Standard deviation
Rationale: Standard deviation is the statistic that quantifies the dispersion of
a dataset relative to its mean. A larger standard deviation indicates greater
variability among the measurements. Coefficient of variation is a relative
measure, and confidence intervals estimate a population parameter.
2. What is the primary purpose of establishing a reference range for a
laboratory analyte?
A) To determine the analytical sensitivity of the test
B) To define the expected values in a healthy population based on normal
distribution
C) To calculate the positive predictive value of the test
D) To identify the presence of systematic analytical error
Correct Answer: To define the expected values in a healthy population based
on normal distribution
Rationale: Reference ranges are typically based on a Gaussian (normal)
distribution, encompassing approximately 95% of values from a healthy
,population. This provides a benchmark for interpreting an individual patient's
result.
3. A laboratory test has a high clinical sensitivity. What does this indicate
about the test?
A) It correctly identifies patients who do not have the disease
B) It correctly identifies patients who have the disease
C) It produces consistent results upon repetition
D) It measures the true value of the analyte
Correct Answer: It correctly identifies patients who have the disease
Rationale: Clinical sensitivity is the ability of a test to correctly identify
patients with a disease (true positive rate). A highly sensitive test is useful
for ruling out a condition when negative.
4. Which type of laboratory error is most likely to occur during the pre-
analytical phase?
A) Air bubbles in the reagent
B) Transcription errors on the final report
C) Improperly filled blood collection tube
D) Deterioration of the photometric light source
Correct Answer: Improperly filled blood collection tube
Rationale: Pre-analytical errors occur before the sample is analyzed and
include issues like patient identification, specimen collection, and handling.
An improperly filled tube is a collection error. Air bubbles and light source
issues are analytical, while transcription errors are post-analytical.
,5. In the context of laboratory testing, what does the term "accuracy" refer
to?
A) The reproducibility of a test result
B) The agreement between a measured value and its true value
C) The ability to detect a target analyte
D) The likelihood of a positive test in a patient with disease
Correct Answer: The agreement between a measured value and its true
value
Rationale: Accuracy describes how close a measured value is to the actual or
"true" value of the analyte. It is distinct from precision, which refers to the
reproducibility of results.
6. A clinician is considering the utility of a diagnostic test for a condition that
has a low prevalence in their practice. Which metric is most important for
them to consider?
A) Analytical sensitivity
B) Clinical specificity
C) Positive predictive value
D) Coefficient of variation
Correct Answer: Positive predictive value
Rationale: Predictive values are dependent on the prevalence of the disease
in the population of interest. In a low-prevalence population, the positive
predictive value decreases, meaning a positive result is more likely to be a
false positive.
, 7. Which of the following is an example of a systematic analytical error?
A) Random air bubbles in a reagent
B) An improperly fitting pipette tip
C) A consistent shift in the mean due to a new reagent lot
D) A one-time power surge affecting the instrument
Correct Answer: A consistent shift in the mean due to a new reagent lot
Rationale: Systematic errors cause a shift in results in one direction (either
consistently high or low). A change in reagent or calibrator lot is a classic
cause. Random errors affect precision unpredictably.
8. What is the coefficient of variation (CV) used to express?
A) The accuracy of a test
B) The precision of a test as a percentage of the mean
C) The clinical sensitivity of a test
D) The confidence interval of the mean
Correct Answer: The precision of a test as a percentage of the mean
Rationale: The coefficient of variation is calculated as (standard deviation /
mean) × 100%. It is a measure of relative variability, often used to compare
the precision of different laboratory methods.
9. According to the principles of diagnostic testing, how are sensitivity and
specificity best characterized?
A) They are dependent on the prevalence of the disease
B) They are used to evaluate a clinical test independent of the population
Practice Psych Mental Health I Q&A | Psychiatric Nursing
1. Which statistical concept describes the spread or variance of a set of
measurements about the mean?
A) Coefficient of variation
B) Confidence interval
C) Standard deviation
D) Gaussian distribution
Correct Answer: Standard deviation
Rationale: Standard deviation is the statistic that quantifies the dispersion of
a dataset relative to its mean. A larger standard deviation indicates greater
variability among the measurements. Coefficient of variation is a relative
measure, and confidence intervals estimate a population parameter.
2. What is the primary purpose of establishing a reference range for a
laboratory analyte?
A) To determine the analytical sensitivity of the test
B) To define the expected values in a healthy population based on normal
distribution
C) To calculate the positive predictive value of the test
D) To identify the presence of systematic analytical error
Correct Answer: To define the expected values in a healthy population based
on normal distribution
Rationale: Reference ranges are typically based on a Gaussian (normal)
distribution, encompassing approximately 95% of values from a healthy
,population. This provides a benchmark for interpreting an individual patient's
result.
3. A laboratory test has a high clinical sensitivity. What does this indicate
about the test?
A) It correctly identifies patients who do not have the disease
B) It correctly identifies patients who have the disease
C) It produces consistent results upon repetition
D) It measures the true value of the analyte
Correct Answer: It correctly identifies patients who have the disease
Rationale: Clinical sensitivity is the ability of a test to correctly identify
patients with a disease (true positive rate). A highly sensitive test is useful
for ruling out a condition when negative.
4. Which type of laboratory error is most likely to occur during the pre-
analytical phase?
A) Air bubbles in the reagent
B) Transcription errors on the final report
C) Improperly filled blood collection tube
D) Deterioration of the photometric light source
Correct Answer: Improperly filled blood collection tube
Rationale: Pre-analytical errors occur before the sample is analyzed and
include issues like patient identification, specimen collection, and handling.
An improperly filled tube is a collection error. Air bubbles and light source
issues are analytical, while transcription errors are post-analytical.
,5. In the context of laboratory testing, what does the term "accuracy" refer
to?
A) The reproducibility of a test result
B) The agreement between a measured value and its true value
C) The ability to detect a target analyte
D) The likelihood of a positive test in a patient with disease
Correct Answer: The agreement between a measured value and its true
value
Rationale: Accuracy describes how close a measured value is to the actual or
"true" value of the analyte. It is distinct from precision, which refers to the
reproducibility of results.
6. A clinician is considering the utility of a diagnostic test for a condition that
has a low prevalence in their practice. Which metric is most important for
them to consider?
A) Analytical sensitivity
B) Clinical specificity
C) Positive predictive value
D) Coefficient of variation
Correct Answer: Positive predictive value
Rationale: Predictive values are dependent on the prevalence of the disease
in the population of interest. In a low-prevalence population, the positive
predictive value decreases, meaning a positive result is more likely to be a
false positive.
, 7. Which of the following is an example of a systematic analytical error?
A) Random air bubbles in a reagent
B) An improperly fitting pipette tip
C) A consistent shift in the mean due to a new reagent lot
D) A one-time power surge affecting the instrument
Correct Answer: A consistent shift in the mean due to a new reagent lot
Rationale: Systematic errors cause a shift in results in one direction (either
consistently high or low). A change in reagent or calibrator lot is a classic
cause. Random errors affect precision unpredictably.
8. What is the coefficient of variation (CV) used to express?
A) The accuracy of a test
B) The precision of a test as a percentage of the mean
C) The clinical sensitivity of a test
D) The confidence interval of the mean
Correct Answer: The precision of a test as a percentage of the mean
Rationale: The coefficient of variation is calculated as (standard deviation /
mean) × 100%. It is a measure of relative variability, often used to compare
the precision of different laboratory methods.
9. According to the principles of diagnostic testing, how are sensitivity and
specificity best characterized?
A) They are dependent on the prevalence of the disease
B) They are used to evaluate a clinical test independent of the population
