TY - JOUR AU - von Hippel, Paul T. PY - 2015 DA - 2015/04/14 TI - The heterogeneity statistic I2 can be biased in small meta-analyses JO - BMC Medical Research Methodology SP - 35 VL - 15 IS - 1 AB - Estimated effects vary across studies, partly because of random sampling error and partly because of heterogeneity. In meta-analysis, the fraction of variance that is due to heterogeneity is estimated by the statistic I2. We calculate the bias of I2, focusing on the situation where the number of studies in the meta-analysis is small. Small meta-analyses are common; in the Cochrane Library, the median number of studies per meta-analysis is 7 or fewer. SN - 1471-2288 UR - https://doi.org/10.1186/s12874-015-0024-z DO - 10.1186/s12874-015-0024-z ID - von Hippel2015 ER -