Module 4 · Lesson 12 of 22
Paired-data tests
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Learning objectives
- Identify legitimate pairing structures.
- Analyse within-pair differences.
- Avoid pseudo-pairing by row order.
Pairing structure
Pairs may be the same garment before/after, the same operator under two methods, or matched units. The test analyses the distribution of within-pair differences, not two independent group means.
Pairing controls unit-to-unit variation when the pair identity is legitimate and preserved.
Garment-factory example
Measure shrinkage on the same panels before and after wash and analyse the paired differences; the pair ID is the panel serial number.
Method
- Define the pair and record the ID.
- Plot the differences.
- Test the mean/median of differences.
- Report CI for the difference and practical effect.
Common mistakes
- Pairing unrelated observations by row order.
- Losing pair IDs during data entry.
Knowledge check
Pick one answer per question. Explanations appear after you submit.
1. A paired test analyses:
2. Pseudo-pairing by row order:
Author: NOSK.life · Last reviewed: 2026-07-21