Page 1 of 80
CLS Exam LATEST UPDATE 2026-2027
QUESTIONS AND CORRECT DETAILED
SOLUTIONS
Question: 29. The percentage of individuals without a specific disease who are correctly
identified or predicted by the test as not having the disease describes
A. Sensitivity
B. Specificity
C. Positive predictive value
D. Negative predictive value - CORRECT ANSWER✔✔B. Specificity
Question: 30. Which of the following terms refers to deviation from the true value caused by
indeterminate errors inherent in every laboratory measurement?
A. Random error
B. Standard error of the mean
, Page 2 of 80
C. Parametric analysis
D. Nonparametric analysis - CORRECT ANSWER✔✔A. Random error
Question: 31. What is the following formula used to
calculate?
(see book for formula)
A. Coefficient of variation
B. Variance
C. Confidence limits
D. Standard deviation - CORRECT ANSWER✔✔D. Standard deviation
Question: 32. Which of the following terms refers to the closeness with which the measured
value agrees with the true value?
A. Random error
, Page 3 of 80
B. Precision
C. Accuracy
D. Variance - CORRECT ANSWER✔✔C. Accuracy
Question: 33. What percentage of values will fall between ±2 s in a Gaussian (normal)
distribution?
A. 34.13%
B. 68.26%
C. 95.45%
D. 99.74% - CORRECT ANSWER✔✔C. 95.45%
Question: 34. Which of the following terms refers to a measure of dispersion or spread of
values around a central value?
A. Range
, Page 4 of 80
B. Validity
C. Variance
D. Coefficient of variation - CORRECT ANSWER✔✔C. Variance
Question: 35. Which of the following describes the ability of an analytical method to maintain
both accuracy and precision over an extended period of time?
A. Reliability
B. Validity
C. Probability
D. Sensitivity - CORRECT ANSWER✔✔A. Reliability
Q: What is the purpose of the preliminary evaluation before fitting contact lenses
Q: What are the six major areas evaluated before fitting contact lenses
A: To determine candidacy for contact lens wear and guide lens selection by evaluating ocular
health, vision, anatomy, and tear film
CLS Exam LATEST UPDATE 2026-2027
QUESTIONS AND CORRECT DETAILED
SOLUTIONS
Question: 29. The percentage of individuals without a specific disease who are correctly
identified or predicted by the test as not having the disease describes
A. Sensitivity
B. Specificity
C. Positive predictive value
D. Negative predictive value - CORRECT ANSWER✔✔B. Specificity
Question: 30. Which of the following terms refers to deviation from the true value caused by
indeterminate errors inherent in every laboratory measurement?
A. Random error
B. Standard error of the mean
, Page 2 of 80
C. Parametric analysis
D. Nonparametric analysis - CORRECT ANSWER✔✔A. Random error
Question: 31. What is the following formula used to
calculate?
(see book for formula)
A. Coefficient of variation
B. Variance
C. Confidence limits
D. Standard deviation - CORRECT ANSWER✔✔D. Standard deviation
Question: 32. Which of the following terms refers to the closeness with which the measured
value agrees with the true value?
A. Random error
, Page 3 of 80
B. Precision
C. Accuracy
D. Variance - CORRECT ANSWER✔✔C. Accuracy
Question: 33. What percentage of values will fall between ±2 s in a Gaussian (normal)
distribution?
A. 34.13%
B. 68.26%
C. 95.45%
D. 99.74% - CORRECT ANSWER✔✔C. 95.45%
Question: 34. Which of the following terms refers to a measure of dispersion or spread of
values around a central value?
A. Range
, Page 4 of 80
B. Validity
C. Variance
D. Coefficient of variation - CORRECT ANSWER✔✔C. Variance
Question: 35. Which of the following describes the ability of an analytical method to maintain
both accuracy and precision over an extended period of time?
A. Reliability
B. Validity
C. Probability
D. Sensitivity - CORRECT ANSWER✔✔A. Reliability
Q: What is the purpose of the preliminary evaluation before fitting contact lenses
Q: What are the six major areas evaluated before fitting contact lenses
A: To determine candidacy for contact lens wear and guide lens selection by evaluating ocular
health, vision, anatomy, and tear film
