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Eins Bernardo wrote:
> > The goal is to investigate the effects of "calcium spray solutions" on > the height of plants. There were four groups of plants in the > experiment. Let A be the control group while B, C and D comprised > the experiemntal group There were three groups in the experimental > group because each group of plants will be sprayed with water > containing 1%, 2% and 3% of calcium. The control group was sprayed > with fresh water ( 0% calcium). More over, for each group, plants > were planted in the 3 pots, with two plants each pot. > > The question is: To investigate if the calcium spray solutions affect > the height of plants, I will use the GLM Univariate with the height > as dependent variable and the group (A, B, C, D) as fixed factor. Do > I include pot in the fixed factor? > > > > > > ------------------------------------------------------------------------ univariate you need to paste the syntax (don't click on OK) and edit the last line to something like this: UNIANOVA.... ... ... ... ... /DESIGN= Group Pot WITHIN Group. HTH, Marta GG ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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I think you would indicate the nesting of Pot within Group like this: /DESIGN= Group Pot(Group). Another option would be to use MIXED, which usually handles random variables better than UNIANOVA or GLM, it seems to me. And of course, you could treat Group as a continuous variable (or "covariate" in SPSS lingo) rather than as a categorical variable (or "factor"). HTH.
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Bruce Weaver bweaver@lakeheadu.ca http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." PLEASE NOTE THE FOLLOWING: 1. My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. 2. The SPSSX Discussion forum on Nabble is no longer linked to the SPSSX-L listserv administered by UGA (https://listserv.uga.edu/). |
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Bruce
This: /DESIGN= Group Pot WITHIN Group. And this: /DESIGN= Group Pot(Group). Are exactly the same. I teach my students both ways, but I like the first because the nesting is clearer. I also teach them MIXED, but they find it more complicated (got mixed...) MGG Bruce Weaver escribió: > García-Granero wrote: > >> Eins Bernardo wrote: >> >>> The goal is to investigate the effects of "calcium spray solutions" on >>> the height of plants. There were four groups of plants in the >>> experiment. Let A be the control group while B, C and D comprised >>> the experiemntal group There were three groups in the experimental >>> group because each group of plants will be sprayed with water >>> containing 1%, 2% and 3% of calcium. The control group was sprayed >>> with fresh water ( 0% calcium). More over, for each group, plants >>> were planted in the 3 pots, with two plants each pot. >>> >>> The question is: To investigate if the calcium spray solutions affect >>> the height of plants, I will use the GLM Univariate with the height >>> as dependent variable and the group (A, B, C, D) as fixed factor. Do >>> I include pot in the fixed factor? >>> >>> >>> >>> >>> >>> ------------------------------------------------------------------------ >>> >> I would include Pot as a random factor, nested within groups. With GLM >> univariate you need to paste the syntax (don't click on OK) and edit the >> last line to something like this: >> >> UNIANOVA.... >> ... >> ... >> ... >> ... >> /DESIGN= Group Pot WITHIN Group. >> >> HTH, >> Marta GG >> >> >> > > I think you would indicate the nesting of Pot within Group like this: > > /DESIGN= Group Pot(Group). > > Another option would be to use MIXED, which usually handles random variables > better than UNIANOVA or GLM, it seems to me. And of course, you could treat > Group as a continuous variable (or "covariate" in SPSS lingo) rather than as > a categorical variable (or "factor"). > > HTH. > > > ----- > -- > Bruce Weaver > [hidden email] > http://sites.google.com/a/lakeheadu.ca/bweaver/ > "When all else fails, RTFM." > > NOTE: My Hotmail account is not monitored regularly. > To send me an e-mail, please use the address shown above. > -- > View this message in context: http://old.nabble.com/GLM-Univariate-tp27634701p27637402.html > Sent from the SPSSX Discussion mailing list archive at Nabble.com. > > ===================== > To manage your subscription to SPSSX-L, send a message to > [hidden email] (not to SPSSX-L), with no body text except the > command. To leave the list, send the command > SIGNOFF SPSSX-L > For a list of commands to manage subscriptions, send the command > INFO REFCARD > > -- For miscellaneous SPSS related statistical stuff, visit: http://gjyp.nl/marta/ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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Hi Marta. I did not know that, but should have known better than to doubt you. ;-) I've never seen the "A WITHIN B" format in the Help files--is it there somewhere? Cheers, Bruce
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Bruce Weaver bweaver@lakeheadu.ca http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." PLEASE NOTE THE FOLLOWING: 1. My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. 2. The SPSSX Discussion forum on Nabble is no longer linked to the SPSSX-L listserv administered by UGA (https://listserv.uga.edu/). |
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Bruce Weaver wrote:
If you click on "Syntax help" icon after pasting UNIANOVA coomand, you can get this:García-Granero wrote: DESIGN Subcommand (UNIANOVA command).. .
nested design,nested design,nested design
UNIANOVA command,UNIANOVA command,UNIANOVA command
Best regards, Marta -- For miscellaneous SPSS related statistical stuff, visit: http://gjyp.nl/marta/ |
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Eins Bernardo wrote:
> How about: > > /DESIGN=Group SET Group*SET. > > How is it differ with your syntax. Is that wrong? > Yes it is. If Pot (SET?) is nested within Group because you have two random pots within each treatment group, then an interaction term is out of the question (wrong from a design point of view: nested items can't interact with their nesting factor). Marta -- For miscellaneous SPSS related statistical stuff, visit: http://gjyp.nl/marta/ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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In reply to this post by E. Bernardo
Eins:
Perhaps I answered too fast because I misunderstood your first description of the layout of your experiment. Tell me if I have the correct picture. You have 4 treatment groups (1 control, 3 increasing doses of Calcium). Each treatment has 3 pots, and each pot has 2 plants. Is that correct? If not, please describe you design with more detail (whether the same pots have plants that receive different treatments, for instance...). Marta ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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In reply to this post by E. Bernardo
Eins Bernardo wrote:
> Why is the posthoc goes like that? > By default, SPSS uses the residual MS to compute Post-hoc tests. In a nested design, since the F test is computed dividing MS(Group) by MS(Set), you need that Post-hoc tests uses the same MS to compute the SE(diff.) for the means comparisons. HTH, Marta > > > > Be careful when running POST-HOC comparisons for Group (in case of > a significant result at Group level): > > /POSTHOC = Group ( TUKEY ) vs Set(Group) > /DESIGN = Group Set(Group). > > Regards, > Marta > > -- For miscellaneous SPSS related statistical stuff, visit: > http://gjyp.nl/marta/ > ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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In reply to this post by Marta Garcia-Granero
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Hi
Eins Bernardo wrote: > > What is the name of the Statistical method that you have suggested? Is > it "between subjects ANOVA" > > Nested ANOVA. Concerning your other question (Group effect significant but Post-Hoc comparisons non significant), can you send the results? Marta -- For miscellaneous SPSS related statistical stuff, visit: http://gjyp.nl/marta/ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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In reply to this post by E. Bernardo
Eins Bernardo wrote:
> Dear Marta, et al. > > You wrote: > >>Concerning your other question (Group effect significant but Post-Hoc > comparisons non significant), can you send the results? > >>Marta > > Please see attachment. > Since the design was balanced, I though it would not be necessary to modify the sum of squares type to 1. With SPSS 15 it would have given the same result, but I see that with 17 (or 18?) it has changed. Use this syntax: UNIANOVA Stem_height BY Group SET /METHOD = SSTYPE(1) /INTERCEPT = INCLUDE /POSTHOC = Group ( TUKEY ) vs Set(Group) /PRINT=DESCRIPTIVE /PLOT = PROFILE( Group ) /CRITERIA = ALPHA(.05) /DESIGN= Group SET(Group). Now the group effect will be non significant (as it should be, given the small diferences between groups as compared to the random fluctuation between Sets) Marta ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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In reply to this post by E. Bernardo
Eins Bernardo wrote:
> I am using version 17. The group is still significant but none of the > pairwise comparison is significant. > Now I realize, for the first time, that you are not treating Set as a random factor. Try this modified version of the syntax: UNIANOVA Stem_height BY Group SET /RANDOM=Set /METHOD = SSTYPE(1) /POSTHOC = Group ( TUKEY ) vs Set(Group) /PRINT=DESCRIPTIVE /PLOT = PROFILE( Group ) /DESIGN= Group SET(Group). If it doesn't give the expected results, then I'll ask for help (from the kind and nice SPSS support people that might be reading this). Marta ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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Eins Bernardo wrote:
> Hi Marta, et al. > > The problem was already solved. Thank you, Marta, for the solution. > > I would like to raise the issue based on what I have discovered a few > days back. > What is the statistical explaination of the instances wherein > the ANOVA is highly significant but none of the posthoc test is > significant? > overall F tests whether there is any difference among any pair of combination of means. For instance, the F could be significant because mean1+mean2 combined differ significantly from mean3+mean4 combined. No post hoc test would reveal that. HTH, Marta GG ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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Scheffe's posttest comparison guarantees at least one significant follow-up test but it controls for all comparisons, both pairwise and complex. Posttest comparisons are not limited to pairwise tests.
Dr. Paul R. Swank, Professor and Director of Research Children's Learning Institute University of Texas Health Science Center-Houston -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Marta García-Granero Sent: Tuesday, March 02, 2010 11:22 AM To: [hidden email] Subject: Re: GLM Univariate Eins Bernardo wrote: > Hi Marta, et al. > > The problem was already solved. Thank you, Marta, for the solution. > > I would like to raise the issue based on what I have discovered a few > days back. > What is the statistical explaination of the instances wherein > the ANOVA is highly significant but none of the posthoc test is > significant? > overall F tests whether there is any difference among any pair of combination of means. For instance, the F could be significant because mean1+mean2 combined differ significantly from mean3+mean4 combined. No post hoc test would reveal that. HTH, Marta GG ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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In reply to this post by Marta Garcia-Granero
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Eins Bernardo wrote:
> Marta wrote: > >>>Post hoc tests focus on pairwise differences between means, while the > overall F tests whether there is any difference among any pair of > combination of means. For instance, the F could be significant because > mean1+mean2 combined differ significantly from mean3+mean4 combined. No > post hoc test would reveal that. > > Is the posthoc you are referring to is true also to post hoc in > one-way anova? > about "classical post-hoc tests" (Tukey ...) is true for any ANOVA design (ONEWAY, nested, repeated measures...). Marta ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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