More Voodoo correlations: when average-based measures inflate correlations.
A Monte-Carlo simulation was conducted to assess the extent that a correlation estimate can be inflated when an average-based measure is used in a commonly employed correlational design. The results from the simulation reveal that the inflation of the correlation estimate can be substantial, up to 76%. Additionally, data was re-analyzed from two previously published studies to determine the extent that the correlation estimate was inflated due to the use of an averaged based measure. The re-analyses reveal that correlation estimates had been inflated by just over 50% in both studies. Although these findings are disconcerting, we are somewhat comforted by the fact that there is a simple and easy analysis that can be employed to prevent the inflation of the correlation estimate that we have simulated and observed.
a King's College London.
Andrew
A
Brand
Michael T
MT
Bradley
D003627:Data Interpretation, Statistical; D006801:Humans; D009010:Monte Carlo Method; D011589:Psychology, Experimental / Q000379:methods / Q000592:standards; D013223:Statistics as Topic / Q000379:methods / Q000592:standards
averaging; correlation; effect size; inflation; reliability