faq

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faq [2020/06/03 23:54] Wolfgang Viechtbauer |
faq [2020/06/26 06:56] (current) Wolfgang Viechtbauer |
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!!! The pseudo $R^2$ statistic (Raudenbush, | !!! The pseudo $R^2$ statistic (Raudenbush, | ||

- | ??? For random-effects models fitted with the rma() function, how is the credibility/prediction interval computed by the predict() function? | + | ??? For random-effects models fitted with the rma() function, how is the prediction interval computed by the predict() function? |

!!! By default, the interval is computed with $$\hat{\mu} \pm z_{1-\alpha/ | !!! By default, the interval is computed with $$\hat{\mu} \pm z_{1-\alpha/ | ||

- | Note that this differs from Riley et al. (2001), who suggest to use a t-distribution with $k-2$ degrees of freedom for constructing the interval. Neither a normal, nor a t-distribution with $k-1$ or $k-2$ degrees of freedom is correct; all of these are approximations. The computations in metafor are done in the way described above, so that the credibility/prediction interval is identical to the confidence interval for $\mu$ when $\hat{\tau}^2 = 0$, which could be argued is the logical thing that should happen. | + | Note that this differs slightly from Riley et al. (2001), who suggest to use a t-distribution with $k-2$ degrees of freedom for constructing the interval. Neither a normal, nor a t-distribution with $k-1$ or $k-2$ degrees of freedom is correct; all of these are approximations. The computations in metafor are done in the way described above, so that the prediction interval is identical to the confidence interval for $\mu$ when $\hat{\tau}^2 = 0$, which could be argued is the logical thing that should happen. |

??? How is the Freeman-Tukey transformation of proportions and incidence rates computed? | ??? How is the Freeman-Tukey transformation of proportions and incidence rates computed? |

faq.txt ยท Last modified: 2020/06/26 06:56 by Wolfgang Viechtbauer

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