within group agreement for nominal/ordinal data

2000-08-22 Thread Ken Reed

I'm trying to test whether a variable measures a group-level property, and
so I'm looking for an analog to eta-squared, intra-class correlation etc for
nominal or ordinal data.

I have data comprising 2000 workplaces, within samples of individuals drawn
from each (n=20,000).

One variable has 4 categories (agree-neutral-disagree, don't know).

1. How can I estimate how much of the total variability derives from between
groups (workplaces) and within groups?

2. Is there a rule-of-thumb for what would be evidence of strong
within-group agreement?

3. Can I do this in SPSS?




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Re: within group agreement for nominal/ordinal data

2000-08-23 Thread Ken Reed


Donald Burrill <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Clarification(s), please:
>
> On Wed, 23 Aug 2000, Ken Reed wrote:
>
> > I'm trying to test whether a variable measures a group-level property,
> > and so I'm looking for an analog to eta-squared, intra-class correlation
> > etc for nominal or ordinal data.
>
> Do you have a particular group-level property in mind, that is measured
> by some variable(s) other than the one you're trying to test?  Or are you
> trying to infer the existence of some such property from the behavior of
> this variable alone (or, perhaps, in concert with others)?

The latter.
>
> > I have data comprising 2000 workplaces, within samples of individuals
> > drawn from each (n=20,000).
>
> Random samples, or convenience samples?  Ten from each workplace, or
> variable (and if variable, why?)?  Do the workplaces assort themselves
> into categories, or are you looking at something like a 1-way ANOVA with
> 2000 groups?

I should have said 'with samples of individuals' not 'within samples of
individuals'.

The workplaces are randomly sampled. Selection of the individuals was based
on a random sample design, but there are known biases.

You've got it -- I'm looking for something analogous to a 1-way ANOVA with
2000 groups, but with a nominal dependent variable.

>
> > One variable has 4 categories (agree-neutral-disagree, don't know).
>
> Are you trying to say that you have one such variable, and your other
> variables are otherwise described;  or that you have a number of such
> variables and you want something like an item analysis of them all;  or
> that you have a number of such variables that you intend to combine in
> some unspecified way to produce the variable you want to test;  or ...?

My question is about just the one variable.
>
> By the way, this variable is not one variable, it is two:  (1) degree of
> agreement with whatever, and (2) whether the respondent has an opinion
> about it.  If you have a bunch of variables like this, what you can do
> with them depends partly on how much missing data (= "don't know"
> responses) you have.
"don't know" is a meaningful response in this case -- it is not 'missing'
data.

>
> > 1. How can I estimate how much of the total variability derives from
> > between groups (workplaces) and within groups?
>
> "Total variability" of one of these 4-category variables, or of a total
> score derived from a bunch of them, or of the bunch of them considered as
> a multivariate whole?

One variable -- the problems analagous to one-way ANOVA, but with a nominal
variable.

>
> > 2. Is there a rule-of-thumb for what would be evidence of strong
> > within-group agreement?
>
> Rules of thumb exist only to help one avoid having to think hard about
> some situation or problem.  As such they are invariably heavily
> dependent on contexts, about which we have very little information.

Perhaps. But they also signal conventions.
>
>  
>  Donald F. Burrill [EMAIL PROTECTED]
>  348 Hyde Hall, Plymouth State College,  [EMAIL PROTECTED]
>  MSC #29, Plymouth, NH 03264 603-535-2597
>  184 Nashua Road, Bedford, NH 03110  603-471-7128
>
>
>
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Guttman reference

2000-09-25 Thread Ken Reed

Guttman wrote a paper, in the 40s I think, called something like: "The four
principal components of a scale". It was re-printed later in an edited book.

Can anyone help with the full reference?




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Re: Double mediation

2001-07-14 Thread Ken Reed

> From: [EMAIL PROTECTED] (Sylvia J. Hysong, Ph.D.)
> Organization: http://groups.google.com/
> Newsgroups: sci.stat.edu,comp.soft-sys.stat.spss
> Date: 5 Jul 2001 14:35:24 -0700
> Subject: Double mediation
> 
> Hello,
> 
> I'm hoping someone can help me with this.  I have looked at a
> multitude of resources including the David Kenny page, this and other
> newsgroups, Pedhazur (1982), Cohen & Cohen (1983), and Darlington
> (1990?), to no avail.  I am hoping someone can direct me to the right
> resource.  I am trying to conduct a test of double mediation.  In
> other words, I am trying to test the hypothesis that x-->z1-->z2-->y.
> Is there a way to do this (and if so, what is it?), or must I result
> to a path analysis or a structural equation model?
> 
> Thanks in advance for any help.

Would this do it?

Estimate a regression model with y as the dependent and x, z1 and z2 as
independents. That gives the direct path from z2-->y, controlling for x and
z1.

Then a second model with z2 as the dependent and x, and z1 as independents.
That gives the direct path from z1-->z2, controlling for x.

The a third model with z1 as the dependent and x as the independent.



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