STP Data Analysis 4

Question 1

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

Accepted Answer

One control value falls outside ±3 SD

Answer

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

Question 2

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

Accepted Answer

True positives divided by (true positives + false negatives)

Answer

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

Question 3

Log transformation of laboratory data is commonly applied to:

Accepted Answer

Positively skewed data to approximate normality

Answer

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

Question 4

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

Accepted Answer

Limit of detection (LOD)

Answer

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

Question 5

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

Accepted Answer

No significant systematic or proportional bias

Answer

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

(STP) Scientist Training Programme Practice Test