Read the document @ http://www.stats.org.uk/statistical-inference/Klay…
Center for Decision Research, Graduate School of Business, University of Chicago
Pychological Review Copyright 1987 by the American Psychological Association, Inc.
1987, Vol. 94, No. 2, 211-228
Strategies for hypothesis testing in scientific investigation and everyday reasoning have interested both psychologists and philosophers. A number of these scholars stress the importance of disconfirmation in reasoning and suggest that people are instead prone to a general deleterious "confirmation bias" In particular it is suggested that people tend to test those cases that have the best chance of verifying current beliefs rather than those that have the best chance of falsifying them. We show, however that many phenomena labeled "confirmation bias" are better understood in terms of a general positive test strategy. With this strategy, there is a tendency to test cases that are expected (or known) to have the property of interest rather than those expected (or known) to lack that property. This strategy is not equivalent to confirmation bias in the first sense; we show that the positive test strategy can be a very good heuristic for determining the truth or falsity of a hypothesis under realistic conditions. It can, however lead to systematic errors or inefficiencies. The appropriateness of human hypotheses-testing strategies and prescriptions about optimal strategies must he understood in terms of the interaction between the strategy and the task at hand.