Statistics laboratory assessment

Learning objectives

• Integrate the Module 9 methods on a mixed garment scenario.
• Choose summaries, tests, charts and capability calculations defensibly.
• Communicate uncertainty in factory language.

Scenario

A polo factory has: measurement variation across inspectors, seam-strength differences between two suppliers, defect proportions on two lines, unstable daily downtime and a proposed 2^3 fusing experiment.

Required work

• Clean and stratify the data using the Module 9 preparation rules.
• Choose summaries and distributions for each variable.
• Compute a confidence interval or effect size per question.
• Fit regression or ANOVA where relevant; run the appropriate test.
• Build I-MR or p chart; assess capability once stability is confirmed.
• Interpret the 2^3 experiment and confirm the chosen setting.

Passing guidance

Answers must state question, variables/units, formulas/free functions, assumptions, result, practical meaning, limitations and action. Numerical answers without design and interpretation are insufficient.

Garment-factory example

Use the polo factory scenario end-to-end; a full pass answers each sub-question with formula, CI, plot reference and a factory action.

Method

1. Read the scenario twice.
2. Draft one page per sub-question using the required work list.
3. Check every answer against the passing guidance and revise weak areas.

Common mistakes

• Reporting p-values without CIs.
• Skipping the stability check before capability.
• Naming tests without explaining assumptions.