Data Analysis Flashcards

The Westgard 1:3s rule in quality control means a run is rejected when:

Answer: One control value falls outside ±3 SD

The 1:3s rule triggers rejection when a single QC result exceeds 3 standard deviations from the mean, indicating a probable error.

In a 2×2 contingency table, which cell value is used to calculate sensitivity?

Answer: True positives divided by (true positives + false negatives)

Sensitivity = TP/(TP+FN), representing the proportion of true disease cases correctly identified by the test.

Log transformation of laboratory data is commonly applied to:

Answer: Positively skewed data to approximate normality

Log transformation compresses the right tail of positively skewed distributions, making them more approximately normal.

Which term describes the smallest concentration of analyte that can be reliably distinguished from zero (blank)?

Answer: Limit of detection (LOD)

The limit of detection (LOD) is the lowest analyte concentration statistically distinguishable from a blank sample with defined confidence.

In a Passing-Bablok regression, the 95% CI for the intercept includes 0 and the slope CI includes 1. This indicates:

Answer: No significant systematic or proportional bias

When the CI for intercept includes 0 and the CI for slope includes 1, neither systematic nor proportional bias is statistically significant.

Which measure is most resistant to the effect of outliers in a dataset?

Answer: Median

The median, as the middle value of ranked data, is unaffected by extreme outliers unlike the mean or variance.

In a laboratory context, 'imprecision' is best quantified by:

Answer: Within-run and between-run coefficients of variation

Imprecision is measured using coefficients of variation from within-run (repeatability) and between-run (reproducibility) studies.