[R-meta] metagen / low heterogeneity
Sean
@e@n@toporek @end|ng |rom gm@||@com
Mon Jan 11 17:45:53 CET 2021
I apologize for the formatting. Here is the ouput and code again
below. I think this should be more readable now that I've selected
plain text.
Michael, well that is good news. If I did have high heterogeneity and
hadn't planned to use a moderator, does that just mean I should
consider looking for one? Whereas in my case, I knew what I was
interested in, so my heterogeneity does not need to be considered as a
prerequisite?
Here is an example of my output:
Number of studies combined: k = 288
SMD 95%-CI t
p-value
Random effects model 0.3309 [ 0.2866; 0.3751] 14.72 < 0.0001
Prediction interval [-0.2216; 0.8834]
Quantifying heterogeneity:
tau^2 = 0.0783 [<0.0000; <0.0000]; tau = 0.2798 [<0.0000; <0.0000];
I^2 = 0.0% [0.0%; 0.0%]; H = 1.00 [1.00; 1.00]
Test of heterogeneity:
Q d.f. p-value
165.46 287 1.0000
Here is the code:
metamkt <- metagen(G,
seG,
data = mkt,
studlab = paste(Study),
comb.fixed = FALSE,
comb.random = TRUE,
method.tau = "SJ",
hakn = TRUE,
prediction = TRUE,
sm = "SMD")
Sean
On Mon, Jan 11, 2021 at 11:11 AM Michael Dewey <lists using dewey.myzen.co.uk> wrote:
>
> Dear Sean
>
> Some comments in-line. It is difficult to read your output because you
> posted in HTML so I will leave that to people more familiar with the
> software. Next time it would help to set your mailer to use plain text
> so your message does not get mangled.
>
> On 11/01/2021 14:56, Sean wrote:
> > Hello Meta-analysis Community,
> >
> > I've been using the metagen function in the meta package for a
> > meta-analysis on fungicide efficacy to control a foliar pathogen in
> > cucumbers. I'm using pre-calculated Hedge's G as my effect size and it's
> > standard error. I'm not really a statistician, so I've been using this
> > resource to hold my hand through the process (
> > https://bookdown.org/MathiasHarrer/Doing_Meta_Analysis_in_R/random.html).
> > I've run into a bit of a rut and I'm having a hard time getting help to
> > interpret my results. I'm dealing with the issue of some of my dataset
> > heterogeneity being nearly 0 (which could just be the case).
> >
> > *Here is an example of my output:*
> >
> > Number of studies combined: k = 288
> >
> > SMD 95%-CI t
> > p-value
> > Random effects model 0.3309 [ 0.2866; 0.3751] 14.72 < 0.0001
> > Prediction interval [-0.2216; 0.8834]
>
> The fact that your prediction interval is so much wider than the
> confidence interval does suggest there is heterogeneity here.
> >
> > Quantifying heterogeneity:
> > tau^2 = 0.0783 [<0.0000; <0.0000]; tau = 0.2798 [<0.0000; <0.0000];
> > I^2 = 0.0% [0.0%; 0.0%]; H = 1.00 [1.00; 1.00]
> >
> > Test of heterogeneity:
> > Q d.f. p-value
> > 165.46 287 1.0000
> >
> > *Here is the code:*
> >
> > metamkt <- metagen(G,
> > seG,
> > data = mkt,
> > studlab = paste(Study),
> > comb.fixed = FALSE,
> > comb.random = TRUE,
> > method.tau = "SJ",
> > hakn = TRUE,
> > prediction = TRUE,
> > sm = "SMD")
> >
> > My first red flag is of course "I^2 = 0.0%", then that my Q p-value is 1.
> > The interpretation being that the observed heterogeneity is completely
> > random. I have a couple datasets, with the highest I^2 = 17.4%. The reason
> > I find it odd, is that when I do subgroup analysis (even though I'm not
> > supposed to with such low / non-existat heterogeneity), the results make
> > biological sense.
>
> No, no, a thousand times no. You use a moderator if there is a
> scientific hypothesis which justifies it not because of observed
> heterogeneity. In this case if there is a biological theory behind a
> moderator then use it.
>
> Michael
>
> My data spans the last decade and the results are also
> > similar with a meta-analysis done in the previous decade on the same topic.
> > This makes me feel like I've made some sort of error at some point in my
> > workflow and I was wondering if you have any diagnostic recommendations for
> > me? One thing that worries me is that my standard errors for my Hedge's G
> > values are so similar since all treatments in each study have 4
> > replications, but maybe it shouldn't.
> >
> > Best,
> >
> > Sean
> >
> > [[alternative HTML version deleted]]
> >
> > _______________________________________________
> > R-sig-meta-analysis mailing list
> > R-sig-meta-analysis using r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-meta-analysis
> >
>
> --
> Michael
> http://www.dewey.myzen.co.uk/home.html
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