Multiply by 37 (or Divide by 0.027): A Surprisingly Accurate Rule of Thumb for Converting Effect Sizes From Standard Deviations to Percentile Points

IF 4.6 Q2 MATERIALS SCIENCE, BIOMATERIALS
Paul von Hippel
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引用次数: 0

Abstract

Educational researchers often report effect sizes in standard deviation units (SD), but SD effects are hard to interpret. Effects are easier to interpret in percentile points, but converting SDs to percentile points involves a calculation that is not transparent to educational stakeholders. We show that if the outcome variable is normally distributed, we can approximate the percentile-point effect simply by multiplying the SD effect by 37 (or, equivalently, dividing the SD effect by 0.027). For students in the middle three-fifths of a normal distribution, this rule of thumb is always accurate to within 1.6 percentile points for effect sizes of up to 0.8 SD. Two examples show that the rule can be just as accurate for empirical effects from real studies. Applying the rule to empirical benchmarks, we find that the least effective third of educational interventions raise scores by 0 to 2 percentile points; the middle third raise scores by 2 to 7 percentile points; and the most effective third raise scores by more than 7 percentile points.
乘以 37(或除以 0.027):将效应大小从标准差转换为百分点的惊人精确的经验法则
教育研究人员通常以标准差单位(SD)来报告效果大小,但标准差效果很难解释。用百分位点来解释效果更容易,但将标准差转换成百分位点需要进行计算,这对教育利益相关者来说并不透明。我们的研究表明,如果结果变量是正态分布的,我们只需将标差效应乘以 37(或等价地将标差效应除以 0.027),就可以得到百分位点效应的近似值。对于处于正态分布中间五分之三的学生来说,这一经验法则对于高达 0.8 SD 的效果大小总是精确到 1.6 个百分位点以内。有两个例子表明,该法则对于实际研究中的经验效果也同样准确。将该法则应用于经验基准,我们会发现,效果最差的三分之一教育干预措施能提高 0 到 2 个百分位点的分数;中间的三分之一能提高 2 到 7 个百分位点的分数;而效果最好的三分之一能提高 7 个百分位点以上的分数。
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来源期刊
ACS Applied Bio Materials
ACS Applied Bio Materials Chemistry-Chemistry (all)
CiteScore
9.40
自引率
2.10%
发文量
464
期刊介绍: ACS Applied Bio Materials is an interdisciplinary journal publishing original research covering all aspects of biomaterials and biointerfaces including and beyond the traditional biosensing, biomedical and therapeutic applications. The journal is devoted to reports of new and original experimental and theoretical research of an applied nature that integrates knowledge in the areas of materials, engineering, physics, bioscience, and chemistry into important bio applications. The journal is specifically interested in work that addresses the relationship between structure and function and assesses the stability and degradation of materials under relevant environmental and biological conditions.
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