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《考研英语阅读理解100篇 基础版》第4章 科学研究类 Unit 57

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2019年01月15日

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Past performance is not an indicator of future returns.That,at least,is the advice given to investors.But can the likelihood of a person committing a crime be predicted by looking at his record? The answer,according to a team of clinical forensic psychologists,is that it cannot.Not only is risk prediction unreliable but,when applied to individuals rather than groups,the margins of error are so high as to render any result meaningless. 
Making assumptions about individuals from group data is generally only reasonably safe when the variation within the group is small.Despite this,risk assessments are routinely used to help decide who should be locked up,who should undergo therapy and who should go free.Risk prediction is also set to be used to assess the threat posed by people ranging from terrorist suspects to potential delinquents. 
Stephen Hart,of Simon Fraser University in British Columbia,Canada,and colleagues decided to determine how accurate the tests of risk assessment are when applied to individuals rather than groups.Typically the tests work by assigning a score to people depending on factors such as their age,the history of their relationships,their criminal past and the type of victims they have chosen.If someone's score places him in a group in which a known proportion has gone on to commit a crime on release from detention,then the risk that person will prove a recidivist is thought to be similar to the risk for the group as a whole. 
The paper published by Dr Hart and his colleagues in last month's issue of the British Journal of Psychiatry focused on two popular tests that follow this logic.The first was a 12-item test designed to assess risk for general violence over periods of seven to ten years.The second was a ten-item test designed to assess risk for violence and sexual violence over periods of five to 15 years.The researchers have also assessed other tests used for predicting sexual offences and domestic violence. 
They found that variations between members of the groups were very large.In one of the tests,for example,the standard estimate of the chances of members of the group sexually reoffending was put at 36% within 15 years.They calculated that the actual range was between 30% and 43% of the group,with a 95% confidence level.But calculating the average probability for a group is much easier than calculating the same probability for any individual.Thus,using standard methods to move from group inferences to individual ones,they calculated that the chance of any one person reoffending was in the range of 3% to 91%,similarly with a 95% confidence level.Clearly,the seemingly precise initial figure is misleading. 
The principle is not peculiar to psychology.It has been recognised by statisticians for decades.They call it the ecological fallacy(although this term captures broader subtleties,too).Medicine has also been confounded by statistically based procedures.Indeed,the technique is only really useful when the successes and failures are aggregated.A life-insurance company,for instance,could wrongly predict the life span of every person it insured but still get the correct result for the group. 
注(1):本文选自Economist; 
注(2):本文习题命题模仿对象为2004年真题Text 4。 
1.What do the clinical forensic psychologists think of risk prediction? 
A) Risk prediction fails in the stock market but succeeds in predicting crime probability. 
B) Risk prediction is always effective when being applied to groups. 
C) Risk prediction is not dependable when it comes to individual behavior. 
D) Risk prediction of groups lacks reliability because of high margin error. 
2.We can learn from the text that tests of risk assessment are _______. 
A) longitudinal 
B) very tricky 
C) convincing enough 
D) unreasonable 
3.What premise did Dr Hart follow when conducting his research? 
A) Two groups should be designed for the tests,with one test group and the other for comparison. 
B) Both risk assessment and risk prediction should be considered in the tests. 
C) People selected for the tests should vary greatly from each other so as to guarantee the representativeness of the sample. 
D) Given small variation within a group,risk prediction for individuals can be based on group data. 
4.According to Dr Hart,using standard methods to predict individuals _______. 
A) is as easy as using them for groups 
B) yields ineffective statistics 
C) can help attain precise results 
D) might be influenced by confidence level 
5.Which of the following statements is TRUE? 
A) Ecological fallacy is originally a psychological phenomenon,which is later adopted in the field of statistics. 
B) Statisticians have been dealing with ecological fallacy for a long time and have almost succeeded in figuring out a solution. 
C) The statistics from a life insurance company on the longevity of a group of people should be reliable. 
D) Risk prediction proves to be of zero practical value according to Dr Hart's study. 

过去的付出并不代表未来的收获,这至少可以给投资者一些启示。但一个人的犯罪动机能通过他过去的记录来预测吗?一个临床法医心理学家小组的回答是否定的。风险预测不仅站不住脚,而且即使是只用于个体而不是群体,其误差之大也会导致结果失去意义。 
只有当一组数据内部差异程度相对较小时,据此做出的对个体的判断通常才会比较可靠。尽管如此,人们还是例行公事地用风险评估来辅助决定谁应该坐牢、谁应该接受治疗以及谁可获得自由。风险预测同样用于评估从嫌疑恐怖分子到潜在罪犯的各种威胁。 
加拿大不列颠哥伦比亚省西蒙弗雷泽大学的斯蒂芬·哈特和他的同事决意要找出用于个体而非群体的风险评估测试的准确性到底有多大。这些测试先根据个人年龄、社交经历、犯罪史以及所选择的受害者类型等因素给人们打出一个分数。如果一个人的分数属于出狱后犯罪率很高的一组,那么此人是惯犯的几率就大体上和这组的整体几率相同。 
哈特博士和他的同事在上月的《英国精神病学杂志》上发表了一篇论文,主要介绍了按照这一逻辑进行的两个有名实验。第一个实验包括12项内容的测试,用来评估7至10年间的一般暴力风险;第二个实验包括10项相关内容的测试,用来评估5至15年间的暴力和性暴力风险。研究人员也评估了用来预测性侵犯和家庭暴力的其他一些测试。 
他们发现每组成员间的差别很大。比如在其中一项测试中,被测小组成员15年内再次进行性侵犯的概率估计是36%。在95%的置信度下,他们计算出的实际范围是在30%与43%之间。但计算群体的平均概率要比计算个体的概率容易得多。因此,如果将群体的标准方法用于个体,同样在95%的置信度下,他们计算出一个人是惯犯的几率在3%与91%之间。很明显,看似准确的原始数据有很大的误导性。 
这个原理不仅专用于心理学,也已被统计学家认可了数十年之久。他们称其为生态学谬论(尽管这个术语还有更广泛和精细的意义)。医学也被基于统计学的程序搞得一团糟。实际上,这个技术只有在成功和失败都综合起来的时候才真正有用。例如,一个人寿保险公司也许不能准确预测每个投保人的寿命长度,但它可以对群体做出准确预测。 
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