Department of Psychology, University of Essex, Colchester, Essex, UK.
Department of Experimental Psychology, Mind, Brain, and Behavior Research Center, University of Granada, Granada, Spain.
Med Decis Making. 2018 Apr;38(3):366-376. doi: 10.1177/0272989X17734203. Epub 2017 Oct 25.
Previous research has shown that format effects, such as the "1-in-X" effect-whereby "1-in-X" ratios lead to a higher perceived probability than "N-in-N*X" ratios-alter perceptions of medical probabilities. We do not know, however, how prevalent this effect is in practice; i.e., how often health professionals use the "1-in-X" ratio.
We assembled 4 different sources of evidence, involving experimental work and corpus studies, to examine the use of "1-in-X" and other numerical formats quantifying probability.
Our results revealed that the use of the "1-in-X" ratio is prevalent and that health professionals prefer this format compared with other numerical formats (i.e., the "N-in-N*X", %, and decimal formats). In Study 1, UK family physicians preferred to communicate prenatal risk using a "1-in-X" ratio (80.4%, n = 131) across different risk levels and regardless of patients' numeracy levels. In Study 2, a sample from the UK adult population ( n = 203) reported that most GPs (60.6%) preferred to use "1-in-X" ratios compared with other formats. In Study 3, "1-in-X" ratios were the most commonly used format in a set of randomly sampled drug leaflets describing the risk of side effects (100%, n = 94). In Study 4, the "1-in-X" format was the most commonly used numerical expression of medical probabilities or frequencies on the UK's NHS website (45.7%, n = 2,469 sentences).
The prevalent use of "1-in-X" ratios magnifies the chances of increased subjective probability. Further research should establish clinical significance of the "1-in-X" effect.
先前的研究表明，格式效应，如“1-in-X”效应——其中“1-in-X”的比例比“N-in-N*X”的比例产生更高的感知概率——会改变对医疗概率的看法。然而，我们不知道这种效应在实践中有多普遍；也就是说，医疗专业人员经常使用“1-in-X”的比例。
我们汇集了 4 种不同的证据来源，包括实验工作和语料库研究，以检查“1-in-X”和其他量化概率的数值格式的使用情况。
我们的研究结果表明，“1-in-X”的使用比例很高，而且医疗专业人员更喜欢这种格式，而不是其他的数值格式（即“N-in-N*X”、%和十进制格式）。在研究 1 中，英国家庭医生在不同的风险水平下，无论患者的计算能力水平如何，都倾向于使用“1-in-X”的比例来传达产前风险（80.4%，n=131）。在研究 2 中，来自英国成年人群体的样本（n=203）报告称，大多数全科医生（60.6%）更喜欢使用“1-in-X”的比例，而不是其他格式。在研究 3 中，在一组随机抽样的描述副作用风险的药物传单中，“1-in-X”的比例是最常用的格式（100%，n=94）。在研究 4 中，在英国国民保健制度网站上，“1-in-X”的格式是最常用的医疗概率或频率的数值表达方式（45.7%，n=2469 个句子）。
“1-in-X”的比例的普遍使用增加了主观概率的可能性。进一步的研究应该确定“1-in-X”效应的临床意义。
