Application of Meta-Analysis to Yield Performance of Rubber (Hevea brasiliensis) Clones

In Hevea, so far no attempt has been made to conduct a meta-analysis on yield performance of clones from many studies. With the objective to demonstrate the application of meta-analysis in Hevea research, yield performance of twelve clones repeated across many trials were subjected to meta-analysis. Two effect-size measures namely Standardised mean difference as Hedge’s g and log response ratio were used for combining results. Standardised mean difference in different studies ranged from −3.76 to 6.83. Random effect mean standardised mean difference in GT1 was 0.38. All the standardised mean difference values in RR1M 600 were negative. In clones RRII203, PB 235, PB 260, PB 217 and PB 311, standardised mean difference values were all positive while in other clones they were mostly negative. Random effect model mean standardised mean difference’s were significantly higher in clones RRII 203 and PB 235. In effect sizes, the percentage change in yield of GT 1 over RRII 105 ranged from negative 13 percent to positive 39 percent.