An example: Meta Analysis with all eligible trials included. Cochrane investigators  were only able to pool two studies to evaluate the effect of Epo on change in hemoglobin in the patients with the baseline level of hemoglobin >12 g/dl who underwent chemotherapy. Their results show that on average Epo increases hemoglobin by 2.05 g/dl. Using our estimation formulas, we were able to include two other studies eligible for this meta-analysis ([9, 10]). The pooled estimate decreased to 1.22 g/dl, i.e., a decrease of approximately 40%.
Hozo et al. BMC Medical Research Methodology 2005 5:13 doi:10.1186/1471-2288-5-13