STP Data Analysis 2 — Questions and Answers
Question 1: In a clinical laboratory study, a Levey-Jennings chart is used primarily to:
- Calculate patient reference ranges
- Monitor quality control over time (Correct answer)
- Determine analyte sensitivity
- Compare two analytical methods
Correct answer: Monitor quality control over time
Levey-Jennings charts plot QC results over time to detect trends, shifts, and random errors in analytical processes.
Question 2: Which statistical test is most appropriate for comparing the means of three or more independent groups?
- Paired t-test
- Chi-square test
- One-way ANOVA (Correct answer)
- Pearson correlation
Correct answer: One-way ANOVA
One-way ANOVA compares means across three or more independent groups simultaneously, controlling the type I error rate.
Question 3: A dataset has a mean of 50 and a standard deviation of 5. What is the coefficient of variation (CV)?
- 5%
- 10% (Correct answer)
- 25%
- 0.1%
Correct answer: 10%
CV = (SD/mean) × 100 = (5/50) × 100 = 10%, expressing variability relative to the mean.
Question 4: When a regression line has a slope of zero, this indicates:
- A perfect positive correlation
- No linear relationship between variables (Correct answer)
- A perfect negative correlation
- High statistical significance
Correct answer: No linear relationship between variables
A slope of zero means changes in the independent variable are not associated with changes in the dependent variable.
Question 5: In Bland-Altman analysis, the limits of agreement are calculated as:
- Mean difference ± 1 SD
- Mean difference ± 2 SD
- Mean difference ± 1.96 SD (Correct answer)
- Median difference ± 2 SD
Correct answer: Mean difference ± 1.96 SD
Limits of agreement are the mean difference ± 1.96 SD, capturing approximately 95% of differences between two methods.
Question 6: Which term describes data that clusters around the middle with few extreme values, resulting in a bell-shaped distribution?
- Bimodal distribution
- Normal distribution (Correct answer)
- Skewed distribution
- Uniform distribution
Correct answer: Normal distribution
A normal (Gaussian) distribution is symmetric and bell-shaped, with most values clustering around the mean.
Question 7: In the STP context, what does 'analytical specificity' refer to?
- The ability of a test to detect all true positives
- The ability of an assay to measure only the intended analyte (Correct answer)
- The minimum detectable concentration of an analyte
- The reproducibility of repeated measurements
Correct answer: The ability of an assay to measure only the intended analyte
Analytical specificity is the ability of an assay to measure only the target analyte without interference from other substances.
STP Data Analysis 2
In a clinical laboratory study, a Levey-Jennings chart is used primarily to: