Date: Sun, 19 Dec 2010 14:01:20 -0800
Reply-To: PetterBB <petter.b.brandtzaeg@GMAIL.COM>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: PetterBB <petter.b.brandtzaeg@GMAIL.COM>
Subject: Re: Can I use time and gender as covariates in Ancova?
In-Reply-To: <4D0E0654.2030100@DrKendall.org>
Content-Type: multipart/alternative;
Thanks, this was helpful, do I need to re-code the age-variable or can I put
all the variables in the analysis as it is?
petter
2010/12/19 Art Kendall [via SPSSX Discussion] <
ml-node+3311098-1984852211-145201@n5.nabble.com<ml-node%2B3311098-1984852211-145201@n5.nabble.com>
>
> I am suggesting that you "control for" all of the sources of variance
> that you have measures for. That is a 4 way ANOVA. Type * Age * Gender
> * time.
>
> It is inefficient not to control for all of the known sources of
> variance. Those sources that are not in the design are therefore in the
> residual (error).
>
> All of the effects in the ANCOVA are in the ANOVA. The ANOVA is more
> complete.
> The ANCOVA controls for only some of the effects of age and gender.
>
> The interaction effects are taken care of by the software when you
> specify the design.
>
> Below there is a simulation of such an analysis, Open a new instance of
> SPSS. copy and paste the syntax. Run it.
> You can generate the syntax via the GUI.
>
> Art Kendall
> Social Research Consultants
>
> * make up some data.
> new file.
> set seed 20101219.
> input program.
> loop id = 1 to 391.
> compute pre = rv.normal(1,1).
> compute mid = pre + rv.normal(1,1).
> compute post = mid + rv.normal(1,1).
> end case.
> end loop.
> end file.
> end input program.
> compute type =1+ mod(id,5).
> compute gender =1+ mod(id,2).
> compute age = rnd(rv.uniform(1,5)).
> formats id (f3) type gender age (f1).
> value labels
> type 1 'a' 2 'b' 3 'c' 4 'd' 5 'e'/
> gender 1 'male' 2 'female'/
> age 1 'first' 2 'second' 3 'third' 4 'fourth' 5 'fifth'.
> *check that there are no empty cells.
> crosstabs tables = type by gender by age.
> * -----------------.
>
> *show the kind of analysis.
>
> * Custom Tables.
> CTABLES
> /VLABELS VARIABLES=type gender age pre mid post DISPLAY=LABEL
> /TABLE type > gender > age + gender BY pre [MEAN] + mid [MEAN] + post
> [MEAN]
> /CATEGORIES VARIABLES=type gender age ORDER=A KEY=VALUE EMPTY=INCLUDE.
>
> GLM pre mid post BY type gender age
> /WSFACTOR=time 3 Polynomial
> /CONTRAST(age)=Polynomial
> /METHOD=SSTYPE(3)
> /PLOT=PROFILE(time time*type time*gender time*age time*age*gender)
> /EMMEANS=TABLES(OVERALL)
> /EMMEANS=TABLES(type) COMPARE ADJ(BONFERRONI)
> /EMMEANS=TABLES(gender) COMPARE ADJ(BONFERRONI)
> /EMMEANS=TABLES(age) COMPARE ADJ(BONFERRONI)
> /EMMEANS=TABLES(time) COMPARE ADJ(BONFERRONI)
> /EMMEANS=TABLES(type*gender)
> /EMMEANS=TABLES(type*age)
> /EMMEANS=TABLES(type*time)
> /EMMEANS=TABLES(gender*age)
> /EMMEANS=TABLES(gender*time)
> /EMMEANS=TABLES(age*time)
> /EMMEANS=TABLES(type*gender*age)
> /EMMEANS=TABLES(type*gender*time)
> /EMMEANS=TABLES(type*age*time)
> /EMMEANS=TABLES(gender*age*time)
> /EMMEANS=TABLES(type*gender*age*time)
> /PRINT=ETASQ OPOWER
> /CRITERIA=ALPHA(.05)
> /WSDESIGN=time
> /DESIGN=type gender age type*gender type*age gender*age type*gender*age.
>
>
>
>
> On 12/18/2010 10:45 AM, PetterBB wrote:
>
> > Art Kendall, thanks, but I am not sure if I understand you.
> >
> > Do you mean it is wrong to use ANCOVA in with my dataset? My main goal is
> to
> > check wether or not different user styles in social networking sites
> imply
> > different types of social capital, by using gender and age as covariates.
>
> >
> > However, if I do the ANOVA the way you suggest, is this done by 2way
> ANOVA
> > or is it 1way? I am not sure how I can control for interaction effects in
>
> > ANOVA the way you are suggesting it? Do you have any good instructions in
>
> > how I can do this?
> >
> > Thanks.
> > Petter
> > --
> > View this message in context:
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>
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--
Petter Bae Brandtzæg
Ustvedtsvei 14b O871 Oslo
Tlf + 4792806546
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