Statistics quiz

Knowledge check

Pick one answer per question. Explanations appear after you submit.

1. 1. CLT states:

   • All data is normal
   • Sampling distribution of the mean tends to normal as n grows, under conditions
   • Median equals mean
   • Variance is zero

2. 2. 95% CI on a small sample uses:

   • z
   • t
   • F
   • Chi-square

3. 3. Cp = 2.0, Cpk = 0.8:

   • Centred and capable
   • Tight but off-centre; defects come from location
   • Bad MSA
   • Wrong spec

4. 4. Excel two-tailed t (equal variance):

   • =CORREL(a,b)
   • =T.TEST(a,b,2,2)
   • =CHISQ.TEST(a,b)
   • =NORM.S.INV(0.975)

5. 5. Regression slope 0.4 mm shrinkage per extra minute of wash:

   • Meaningless
   • Means each additional minute of wash increases shrinkage by ~0.4 mm on average
   • Causes shrinkage
   • R² = 1

6. 6. ANOVA compares:

   • Two proportions
   • Means across three or more groups
   • Variances only
   • Categorical data

7. 7. Rational subgroups should:

   • Mix all conditions
   • Group items produced under similar conditions to expose between-group variation
   • Ignore time
   • Use only outliers

8. 8. Gage R&R above 30% means:

   • Excellent MSA
   • Unacceptable — fix measurement before continuing
   • Marginal
   • Ignore

9. 9. Statistical significance without practical significance is:

   • Success
   • A large-sample artefact that may not justify a change
   • Failure
   • A p-hacking violation

10. 10. A conclusion should include:

    • Only the p-value
    • Question, design, assumptions, effect, uncertainty and factory interpretation
    • Only the effect
    • Only the recommendation