[R-meta] About whether to delete the outliers from the dataset

[Michael Dewey]

Dear Nick

Apart from the two options you outline (include all, exclude four) I 
assume you have already investigated whether these four studies share 
some common feature which might explain the differences.

I would suggest presenting the full analysis as your main one and then 
presenting the one excluding the four as a sensitivity analysis. If the 
scientific conclusions are unaltered then your discussion is much 
simpler but if excluding them leads to a different conclusion then your 
discussion section needs to provide some suggestion about what is going on.

I think presenting the analysis excluding the four as the main analysis 
is less preferable and, of course, just reporting that analysis and 
ignoring the four altogether is clearly wrong (I know you did not 
suggests that).

Michael

On 10/12/2023 06:32, Nick Chen via R-sig-meta-analysis wrote:
> I have a question concerning whether to delete some of the data or not. I
> have a dataset of 56 studies with a pooled effect size of g=1.25. Yet,
> there are 4 data that reported an incredibly high effect size (8.15, 6.63,
> 4.14, 4.10 respectively). Statistically, they should be considered as
> outliers and be removed from the dataset. But since these data went through
> the inclusion and exclusion criteria, they should be staying in the dataset
> since they met all the requirements of my selection. So if we excluded the
> 4 data, wouldn't that be miss-reporting some data in the dataset? What
> should I do? Should I excluded the 4 seemingly influential cases or keep
> them for a complete list of research?
> *Name*: Nick Chen (Ping-Cheng, Chen)
> *School*:National Taiwan Normal University (NTNU) English Department
> (Master)
> *Email*: wow99308008 using gmail.com
> *Phone number*: +886 909 663 963
> 
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-- 
Michael