analyses:berkey1995
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analyses:berkey1995 [2021/10/06 15:48] – Wolfgang Viechtbauer | analyses:berkey1995 [2022/10/19 18:55] (current) – Wolfgang Viechtbauer | ||
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Berkey et al. (1995) describe the meta-analytic random- and mixed-effects models and provide the equation for the empirical Bayes estimator for the amount of (residual) heterogeneity (p. 398). The models and methods are illustrated with the BCG vaccine dataset (Colditz et al., 1994). The data are provided in Table 1 in the article and can be loaded with: | Berkey et al. (1995) describe the meta-analytic random- and mixed-effects models and provide the equation for the empirical Bayes estimator for the amount of (residual) heterogeneity (p. 398). The models and methods are illustrated with the BCG vaccine dataset (Colditz et al., 1994). The data are provided in Table 1 in the article and can be loaded with: | ||
+ | |||
<code rsplus> | <code rsplus> | ||
library(metafor) | library(metafor) | ||
dat.bcg | dat.bcg | ||
</ | </ | ||
- | The contents of the dataset are: | + | The contents of the dataset are: |
<code output> | <code output> | ||
| | ||
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Model Results: | Model Results: | ||
- | estimate | + | estimate |
- | | + | |
--- | --- | ||
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These results match exactly what Berkey et al. (1995) report on page 408: The amount of heterogeneity (' | These results match exactly what Berkey et al. (1995) report on page 408: The amount of heterogeneity (' | ||
- | ==== Mixed-Effects Model ==== | + | ==== Mixed-Effects |
- | A mixed-effects model with absolute latitude as moderators (centered at 33.46 degrees) can be fitted with: | + | A mixed-effects |
<code rsplus> | <code rsplus> | ||
res.ME <- rma(yi, vi, mods=~I(ablat-33.46), | res.ME <- rma(yi, vi, mods=~I(ablat-33.46), | ||
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Model Results: | Model Results: | ||
- | estimate | + | estimate |
- | intrcpt | + | intrcpt |
- | I(ablat - 33.46) | + | I(ablat - 33.46) |
--- | --- | ||
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<code output> | <code output> | ||
df | df | ||
- | Full 3 29.3011 30.9960 31.9678 -11.6506 | + | Full 3 29.3011 30.9960 31.9678 -11.6506 |
Reduced | Reduced | ||
</ | </ | ||
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</ | </ | ||
- | ==== Fixed-Effects Model ==== | + | ==== Fixed-Effects |
- | The results from a fixed-effects model with absolute latitude as the predictor can be obtained with: | + | The results from a fixed-effects |
<code rsplus> | <code rsplus> | ||
res.FE <- rma(yi, vi, mods=~I(ablat-33.46), | res.FE <- rma(yi, vi, mods=~I(ablat-33.46), | ||
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Model Results: | Model Results: | ||
- | estimate | + | estimate |
- | intrcpt | + | intrcpt |
- | I(ablat - 33.46) | + | I(ablat - 33.46) |
--- | --- | ||
- | Signif. codes: | + | Signif. codes: |
</ | </ | ||
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</ | </ | ||
<code output> | <code output> | ||
- | pred ci.lb ci.ub | + | pred ci.lb ci.ub |
- | 1 0.55 0.48 0.63 | + | 1 0.55 0.48 0.63 |
2 0.43 0.36 0.52 | 2 0.43 0.36 0.52 | ||
</ | </ |
analyses/berkey1995.txt · Last modified: 2022/10/19 18:55 by Wolfgang Viechtbauer