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The Problem with Magnitude-based Inference

delete2018-10-01
delete93
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OA
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K
Kristin L. Sainani *
DOI:10.1249/MSS.0000000000001645delete
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Abstract

Abstract

En 中文
Purpose A statistical method called magnitude-based inference (MBI) has gained a following in the sports science literature, despite concerns voiced by statisticians. Its proponents have claimed that MBI exhibits superior type I and type II error rates compared with standard null hypothesis testing for most cases. I have performed a reanalysis to evaluate this claim. Methods Using simulation code provided by MBI's proponents, I estimated type I and type II error rates for clinical and nonclinical MBI for a range of effect sizes, sample sizes, and smallest important effects. I plotted these results in a way that makes transparent the empirical behavior of MBI. I also reran the simulations after correcting mistakes in the definitions of type I and type II error provided by MBI's proponents. Finally, I confirmed the findings mathematically; and I provide general equations for calculating MBI's error rates without the need for simulation. Results Contrary to what MBI's proponents have claimed, MBI does not exhibit superior type I and type II error rates to standard null hypothesis testing. As expected, there is a tradeoff between type I and type II error. At precisely the small-to-moderate sample sizes that MBI's proponents deem optimal, MBI reduces the type II error rate at the cost of greatly inflating the type I error rateto two to six times that of standard hypothesis testing. Conclusions Magnitude-based inference exhibits worrisome empirical behavior. In contrast to standard null hypothesis testing, which has predictable type I error rates, the type I error rates for MBI vary widely depending on the sample size and choice of smallest important effect, and are often unacceptably high. Magnitude-based inference should not be used.
Keywords:
TYPE I ERROR
TYPE II ERROR
HYPOTHESIS TESTING
CONFIDENCE INTERVALS
STATISTICS
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Journal

M
Medicine and Science in Sports and Exercise
IF:
3.9
Papers:
4.6K
Citations:
3.9W

Organization

S
Stanford University
Scholars:
9.6W
Papers: 8.2W
Citations: 17.0W