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Table 1 Summary of the four meta-analysis examples

From: Confidence intervals for the between-study variance in random-effects meta-analysis using generalised heterogeneity statistics: should we use unequal tails?

Meta k I 2 \(\hat {\tau }^{2}\) Equal- α W-optimal \(\alpha ^{*}_{2}\) Width
Analysis     CI interval   Ratio
CERVIX3 5 56 % 0.087 (0, 1.660) (0, 1.100) 0.050 0.662
NSCLC4 11 75 % 0.132 (0.052, 0.787) (0.021, 0.638) 0.048 0.839
NSCLC1 17 45 % 0.024 (0.000, 0.181) (0, 0.147) 0.050 0.815
CERVIX1 18 62 % 0.112 (0.041, 0.500) (0.017, 0.427) 0.046 0.892
  1. I2 is the heterogeneity statistic of Higgins and Thompson [28] and \(\hat {\tau }^{2}\) is the DerSimonian and Laird estimate. In each case we show the equal tailed (α1=α2=0.025) 95 % confidence interval, the W-optimal interval, the value of \(\alpha ^{*}_{2}\) that provides the W-optimal interval and the ratio of the width of the W-optimal interval and the equal tailed confidence interval. In each case we see that there is substantial reduction in the interval width by adopting α2>>α1