Page 305 - Six Sigma Demystified

Part 3 s i x s i g m a to o l s 285

Hypothesis Tests on One-Sample Variance

Minitab

Menu: Stat\Basic Stats\1 Variance

Check Perform hypothesis test; enter σ .
0
“Options” button: Set Confidence Level 1 – α and alternative Not Equal (two-
sided case) or > or < (for one-sided cases).

Two-Sided Example at 5% Significance
Method Chi-square df p Value

Standard 12.90 14 0.932
Conclude: Fail to reject (p > 0.05).

One-Sided Example at 5% Significance: Case 1 (Using Alternative
less than):
Method Chi-square df p Value

Standard 12.90 14 0.466
Conclude: Fail to reject null (p > 0.05).

Excel

Calculate p as
Two-sided:
If CHIDIST≤0.5: 2*(CHIDIST(χ ,n-1))
0
If CHIDIST>0.5: 2*(1-CHIDIST(χ ,n-1))
0
One-sided Case 1: 1-CHIDIST(χ ,n-1)
0
One-sided Case 2: CHIDIST(χ ,n-1)
0
Two-Sided Example at 5% Significance
=2*(1-CHIDIST(12.88,14)); p = 0.928; fail to reject.

One-Sided Example at 5% Significance (Case 1)
=1-CHIDIST(12.88,14); p = 0.464; fail to reject.