《考研英語閱讀理解100篇 基礎版》第4章　科學研究類 Unit 57

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）：本文選自Economist； 
注（2）：本文習題命題模仿對象為2004年真題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.