```Date: Tue, 2 Sep 2003 10:19:04 +0200 Reply-To: Asesoría Bioestadística Sender: "SPSSX(r) Discussion" From: Asesoría Bioestadística Subject: Re: ANOVA or Kruskal-Wallis ANOVA Content-Type: text/plain; charset=us-ascii > Marta, in response to your questions about: > > - Every sample size (not just the total sample size) > - Skewness/Kurtosis for every sample > > Here it is: > > Group A (n=17) Mean= 8.76 (SD=4.42) Min, Max (2,16) > Skewness= -0.087 (SE=0.550) Kurtosis =-1.256 (SE=1.06) > Normality: Shapiro Wilk .937, df=17, p=0.281 > > Group B (n=22) = 5.50 (SD=2.60) Min, Max (1,12) > Skewness= 0.611 (SE=0.491) Kurtosis =0.649 (SE=0.95) > Normality: Shapiro Wilk .957, df=22, p=0.425 > > Group C (n=8) Mean=6.50 (SD=4.24) Min, Max 0 12 > Skewness= -0.539 (SE=0.752) Kurtosis =-0.863 (SE=1.48) > Normality: Shapiro Wilk .937, df=8, p=0.580 > > Group D (n=26) Mean=5.08 (SD=3.10) Min, Max 1,12 > Skewness= 0.613 (SE=0.456) Kurtosis =-0.203 (SE=0.887) > Normality: Shapiro Wilk .934, df=26 p=0.099 > > 1) By the way, what is the difference between Shapiro Wilk & the Kolmogorov-Smirnov > Test? Montecarlo simulations have shown that Shapiro-Wilk test is better than K-S(Lilliefors). > 2) So within each group, the p-value is not significant for the normality test so the > hypothesis of normality cannot be rejected > > 3) Levene Test 3.17, df1=3, df2=69, p=0.030 > > Homogeneity of variances was rejected > > So - do you think a case can be made using ANOVA and then the Tamhane test? Yes, use Welch or Brown-Forsythe test (if you have SPSS11.x) instead of ordinary ANOVA. Remember that Tamhane test is highly conservative. If you want something more sensitive use contrasts and decide which p-value adjustment you are going to use. This is the coefficient matrix for the contrasts: -1 1 0 0 -1 0 1 0 -1 0 0 1 0 -1 1 0 0 -1 0 1 0 0 -1 1 > Also - when I ran this, the p-values the output provides are not adjusted for multiple > comparisons, correct? Are you talking about Tamhane test. It is already adjusted (and heavily, too). Only contrasts are not adjusted in any way. Regards Marta Garcia-Granero ```

Back to: Top of message | Previous page | Main SPSSX-L page