[R-sig-ME] Confidence interval for sum of coefficients

[Michael Cone]

Dear Lorenz,

ah, thank you for pointing this out, I really should have read the list 
more carefully. I will look into the relevant conversation.

Kind regards
Michael

Am 25.09.2014 14:35 schrieb lorenz.gygax at agroscope.admin.ch:
> Dear Michael,
> 
> This is possibly not what you should do. As has been recently
> suggested to me on this list, you could use bootMer with a function
> that computes the sum(s) that you are interested in. Then use boot.ci
> from the boot package to estimate the confidence intervals
> 
> Best wishes, Lorenz
> 
>> -----Ursprüngliche Nachricht-----
>> Von: r-sig-mixed-models-bounces at r-project.org 
>> [mailto:r-sig-mixed-models-
>> bounces at r-project.org] Im Auftrag von Michael Cone
>> Gesendet: Donnerstag, 25. September 2014 14:11
>> An: r-sig-mixed-models at r-project.org
>> Betreff: [R-sig-ME] Confidence interval for sum of coefficients
>> 
>> Hello,
>> 
>> I suspect this to be simple, but I can't figure it out.
>> 
>> > library(lme4)
>> > data(Machines)
>> > fm1 <- lmer(score ~ Machine + (Machine | Worker), data = Machines)
>> > summary(fm1)
>> Fixed effects:
>>              Estimate Std. Error t value
>> (Intercept)   52.356      1.681  31.151
>> MachineB       7.967      2.421   3.291
>> MachineC      13.917      1.540   9.036
>> > confint(fm1)
>>                   2.5 %     97.5 %
>> [...]
>> (Intercept) 48.7964047 55.9147119
>> MachineB     2.8401623 13.0931789
>> MachineC    10.6552809 17.1780575
>> 
>> [and 14 warnings, but it's just an example:
>> In optwrap(optimizer, par = start, fn = function(x) dd(mkpar(npar1,  
>> ...
>> :
>> convergence code 1 from bobyqa: bobyqa -- maximum number of function
>> evaluations exceeded
>> ...
>> In profile.merMod(object, signames = oldNames, ...) : non-monotonic
>> profile]
>> 
>> I'd like to have confidence intervals for the overall score of 
>> MachineA,
>> MachineB, and MachineB. MachineA is easy (CI of the intercept), but 
>> how
>> do I combine the CI of the intercept with the CI of the MachineB
>> parameter, and likewise the CI of the intercept with the parameter of
>> MachineC? Can I simply add the lower and upper bounds of the two
>> intervals or is this naive?
>> 
>> Thank you for your time,
>> 
>> Michael
>> 
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