[R-meta] FW: Welcome to the "R-sig-meta-analysis" mailing list (Digest mode) _ question
Tetyana Kendzerska
kendzer@k@y@ @end|ng |rom gm@||@com
Wed Sep 18 05:40:53 CEST 2019
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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