[Mediation-information] Nonparametric Bootstrap

[Teppei Yamamoto]

Hi Lawrence,

We've slightly changed the way p-values are calculated as of Version 
4.1.1, which on my record was released on August 23, 2012. This change 
will generally not make big differences, except when your effect 
estimates are very close to zero (to the extent that R cannot tell the 
difference for some of your bootstrap draws) and/or when the bootstrap 
distributions are highly asymmetric.

We didn't change the way confidence intervals are calculated, so I do 
not have a good sense of what could have gone wrong there.

Best,
Teppei

(3/11/13 3:39 PM), Lawrence Ngo wrote:
> Dear Dr. Imai,
>
> Thanks so much for putting together this useful mediation package. I
> have been having an issue re-running a nonparametric bootstrap mediation
> analysis. Comparing notes from the old and new analysis that I am doing
> on the same data (and both using 10000 simulations), it looks like the
> confidence intervals and p-values are different across the two analyses.
> I am fairly confident that nothing has changed in my data, since all of
> the parameter estimates are identical across old and new.
>
> Do you have any insight on why this may be the case? I ran the old
> analysis around 6 months ago. Thanks in advance for you help!
>
> Best,
> Lawrence
>
>
>
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-- 
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Teppei Yamamoto
Assistant Professor
Department of Political Science
Massachusetts Institute of Technology
http://web.mit.edu/teppei/www/
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