### Abstract

A traditional measure of effect size associated with tests for difference between two groups is the variance explained by group membership (R-2). If exposure to a disease causes a small but long term deficit in performance, however, R-2 does not capture that cumulating effect. We propose an alternative statistic, gamma, based on the probability of an unexposed person outperforming an exposed person. Although gamma is also a point estimate, it more easily conveys what the cumulating effect of a deficit would be. We discuss some of the advantages of this measure. Copyright (C) 2000 John WiIey & Sons, Ltd.

Original language | English |
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Pages (from-to) | 1295-1302 |

Number of pages | 8 |

Journal | Statistics in Medicine |

Volume | 19 |

Issue number | 10 |

DOIs | |

Publication status | Published - 30 May 2000 |

Externally published | Yes |

## Cite this

Reidpath, D. D., Diamond, M. R., Hartel, G., & Glasziou, P. (2000). Improving interpretability: Gamma as an alternative to R-2 as a measure of effect size.

*Statistics in Medicine*,*19*(10), 1295-1302. https://doi.org/10.1002/(SICI)1097-0258(20000530)19:10<1295::AID-SIM493>3.0.CO;2-Z