[R-meta] Moderator level getting removed from model
Michael Dewey
lists at dewey.myzen.co.uk
Tue Feb 13 10:12:09 CET 2018
Dear Shannon
Perhaps I misunderstand you but why not just put a footnote in your
table explaining why there is no estimate? You might want to clarify
there whether this zero is a structural zero (in principle is zero) or a
sampling zero (could have been positive but in your data is zero).
Michael
On 12/02/2018 21:08, Shannon Duncan wrote:
> Hi Wolfgang,
>
> The table does reveal that there are no observations for the "1" coded in
> Decision Aids for the 2 tridiff level.
>
> We're essentially yes looking for a way to show this is in the reporting of
> the meta analysis.
>
> Thank!
> Shannon
>
> 0 1
> 1 32 12
> 2 10 0
> 3 11 12
>
>
>
> On Mon, Feb 12, 2018 at 12:56 PM, Viechtbauer Wolfgang (SP) <
> wolfgang.viechtbauer at maastrichtuniversity.nl> wrote:
>
>> Dear Shannon,
>>
>> Indeed, rma() will omit a coefficient from the model if it is not
>> estimable. What does
>>
>> table(choiceaccdata$tridiff, choiceaccdata$Provides.Decision.Aids)
>>
>> show? I suspect this will reveal why this coefficient is not estimable.
>>
>> So the only thing one could print for that coefficient would be NA (not
>> available). Are you looking for a way to show this?
>>
>> Best,
>> Wolfgang
>>
>>> -----Original Message-----
>>> From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-
>>> project.org] On Behalf Of Shannon Duncan
>>> Sent: Monday, 12 February, 2018 18:23
>>> To: r-sig-meta-analysis at r-project.org
>>> Subject: [R-meta] Moderator level getting removed from model
>>>
>>> Hello,
>>>
>>> I have a question that I can't seem to find an answer to, hoping someone
>>> here can help me out. We are running the following model:
>>>
>>> resalt <- metafor::rma(cohens_d, variance, mods = ~ factor(tridiff) *
>>> Provides.Decision.Aids, test = "t", data = choiceaccdata)
>>>
>>> resalt
>>>
>>> ## tau^2 (estimated amount of residual heterogeneity): 0.0574 (SE =
>>> 0.0175)
>>> ## tau (square root of estimated tau^2 value): 0.2395
>>> ## I^2 (residual heterogeneity / unaccounted variability): 67.78%
>>> ## H^2 (unaccounted variability / sampling variability): 3.10
>>> ## R^2 (amount of heterogeneity accounted for): 39.40%
>>> ##
>>> ## Test for Residual Heterogeneity:
>>> ## QE(df = 72) = 195.8927, p-val < .0001
>>> ##
>>> ## Test of Moderators (coefficient(s) 2:5):
>>> ## F(df1 = 4, df2 = 72) = 6.8504, p-val < .0001
>>> ##
>>> ## Model Results:
>>> ##
>>> ## estimate se tval
>>> pval
>>> ## intrcpt -0.2234 0.0527 -4.2434
>>> <.0001
>>> ## factor(tridiff)2 -0.1642 0.1415 -1.1609
>>> 0.2495
>>> ## factor(tridiff)3 -0.4823 0.1523 -3.1656
>>> 0.0023
>>> ## Provides.Decision.Aids 0.2183 0.0996 2.1910
>>> 0.0317
>>> ## factor(tridiff)3:Provides.Decision.Aids 0.6595 0.2218 2.9736
>>> 0.0040
>>> ## ci.lb ci.ub
>>> ## intrcpt -0.3284 -0.1185 ***
>>> ## factor(tridiff)2 -0.4462 0.1178
>>> ## factor(tridiff)3 -0.7860 -0.1786 **
>>> ## Provides.Decision.Aids 0.0197 0.4169 *
>>> ## factor(tridiff)3:Provides.Decision.Aids 0.2174 1.1017 **
>>>
>>> As you can see, it's not showing the second level of the factor tridiff
>>> (tridiff2) interacting with Decision Aids. I realise this is probably due
>>> to redundancy or something of that sort, but we would like to see it
>>> printed out. Is that at all possible?
>>>
>>> Thank you for your time and any insight you can provide,
>>> Shannon
>>
>
>
>
--
Michael
http://www.dewey.myzen.co.uk/home.html
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