[R-meta] Problem with predict.rma, was Re: FW: Welcome to the "R-sig-meta-analysis" mailing list (Digest mode) _ question

[Michael Dewey]

Dear Tetyana

Have you looked at the Riley et al paper referenced in the 
documentation? I think it has the formula although I have not time to 
check that now.

Michael

On 18/09/2019 04:40, Tetyana Kendzerska wrote:
> Dear All,
> 
> I am wondering if you can help me understanding the underlaying
> calculations/formula for the confidence intervals (both) using the
> predic.rma function.
> 
> I will try to explain the situation using an example below.
> 
>> test_TST = rma(yi=TST_Mean, sei=TST_E, method="DL",
> mods=~Age_Mean+Sex__1+Night_coded, data=moderators[-c(5,69,117,168), ])
>> test_TST
> 
> Mixed-Effects Model (k = 128; tau^2 estimator: DL)
> 
> tau^2 (estimated amount of residual heterogeneity):  439.3101 (SE =
> 263.3751) tau (square root of estimated tau^2 value):             20.9597
> I^2 (residual heterogeneity / unaccounted variability): 91.95%
> H^2 (unaccounted variability / sampling variability):   12.42
> R^2 (amount of heterogeneity accounted for):            70.67%
> 
> Test for Residual Heterogeneity:
> QE(df = 124) = 1539.9995, p-val < .0001
> 
> Test of Moderators (coefficient(s) 2,3,4):
> QM(df = 3) = 183.5661, p-val < .0001
> 
> Model Results:
> 
>   		estimate       se     	zval    pval     ci.lb
> ci.ub
>   intrcpt      	375.7589  10.4376  36.0005  <.0001  355.3016  396.2162  ***
> Age_Mean      	-1.0134     0.1345    -7.5366  <.0001   -1.2770   -0.7499
> ***
> Sex__1           	0.0291       0.0667    0.4365  0.6624   -0.1017
> 0.1599
> Night_coded     38.3012     4.5223     8.4694  <.0001   29.4376   47.1647
> ***
> 
> ---
> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
> 
> I am trying to predict the estimates for the outcome, TST, based on certain
> parameters using the predic.rma function:
> 
>> predict.rma (test_TST, newmods=cbind(c(65),c(100),c(1)))
>       pred     se    		ci.lb    ci.ub    cr.lb    	cr.ub
> 351.1013 5.3417 340.6318 361.5708 308.7079 393.4947
> 
> 
> My question is how I can use estimates from the rm () model results above
> (the formula) to get the ci.lb    ci.ub    cr.lb    cr.ub manually?
> 
> To get pred value, we used the following formula which makes sense:
> Intercept_estimate + Age_coeff_estimate X Age (65) +Sex_coeff_estimate X 0
> [if women] or 100 [if men] +  Sleep_Night_coeff_estimate X 0 [first night]
> or 1 [second night].
> 
> Which formula we should use to get in the same way:  ci.lb    ci.ub    cr.lb
> cr.ub?
> 
> Thank you in advance and sorry if it sounds somewhat confusing,
> Tetyana
> 
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html