Module 4 · Lesson 11 of 22
One-sample and two-sample mean tests
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Learning objectives
- Choose between one-sample and two-sample t-tests.
- Check assumptions and report the effect interval.
- Recognise when Welch’s method is appropriate.
Structure
- One-sample H0: μ = target.
- Two-sample H0: μ1 − μ2 = 0.
- Independent observations; representative samples.
- Welch’s method when variances differ.
Garment-factory example
Test whether mean SPI meets the standard, or compare average operation time between two independent methods with N=30 per group.
Method
- Plot the data and check independence.
- Compute t, p-value and CI in a spreadsheet.
- Report the estimated difference with units.
- Compare the effect with the practical threshold.
Common mistakes
- Using a two-sample test on paired garments.
- Ignoring subgroup and time structure.
Knowledge check
Pick one answer per question. Explanations appear after you submit.
1. Welch’s t-test is preferred when:
2. Reporting only the p-value:
Author: NOSK.life · Last reviewed: 2026-07-21