```Date: Mon, 5 Sep 2005 22:21:45 -0400 Reply-To: "Frank J. Gallo" Sender: "SPSSX(r) Discussion" From: "Frank J. Gallo" Subject: Re: ANOVA and Post-hoc Tests Comments: To: Isaac Dialsingh In-Reply-To: <015e01c5b27d\$38aa7b00\$63076cc8@datatrend> Content-Type: text/plain; charset="US-ASCII" Hi Isacc, Fisher's LSD test does not correct for multiple comparisons as the Tukey HSD post test does. Tukey HSD sets the 5% significance level for the entire family of comparisons. Generally, researchers do not recommend Fisher's LSD test but Tukey's HSD. This is my understanding. Thanks, Frank -----Original Message----- From: Isaac Dialsingh [mailto:consult@tstt.net.tt] Sent: Monday, September 05, 2005 8:51 PM To: Frank J. Gallo Subject: Re: ANOVA and Post-hoc Tests Why didn't you use the LSD test? Isaac ----- Original Message ----- From: "Frank J. Gallo" Newsgroups: bit.listserv.spssx-l To: Sent: Monday, September 05, 2005 3:19 PM Subject: ANOVA and Post-hoc Tests > Hi All, > > > > Looking for some help on interpreting contradictions found in an ANOVA run > with TukeyHSD follow-up. The F-test indicates significant differences among > groups. > > > > ANOVA > > > > > Sum of Squares > > df > > Mean Square > > F > > Sig. > > > > Between Groups > 2.849 > > 3 > > .950 > > 2.830 > > .041 > > > > Within Groups > 46.649 > > 139 > > .336 > > > > > > > > Total > 49.498 > > 142 > > > > > > > > > > > > > > Levene = 5.168, p=.002, the null hypothesis that the error variance of the > dependent variable is equal across groups suggests no. > > But, post-hoc comparisons show no significant differences among groups. > > And, the homogenous subsets table identifies one set (4 groups, p=.143) > indicating that the means of the subgroups are not significantly different > from each other. > > > > I do have unequal sample sizes: 23, 42, 30, 48. The run used the harmonic > mean (32.934), so I am aware that the Type 1 error level is not guaranteed. > Is this what I am seeing? That is, the p-value for the F-test is > underestimated and it should be larger. This is my first experience with > this kind of situation. > > > > Yours thoughts are greatly appreciated. > > Frank ```

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