假設檢定歷程中機率模式探討

Abstract

人在假設檢定時不易證偽。Kirby的信號偵測理論（1994）認為人其實有證偽的能力，但假設（若P則Q）中P與Q的機率大小會影響受試者假設檢定的方式，他預測當先行條件P的機率愈大時，證偽的情形將會上升。Oaksford和Chater（1996）的最佳資料選擇理論則不假設人有證偽的能力，他們認為受試者傾向選擇測試後果所提供的預期資訊增加量較大的方案。本研究使用Wason的選卡片作業來探討先行條件P與後果Q的機率大小對假設檢定歷程的影響。實驗中操弄：P及Q的機率大小、及題目中是否提示受試者規則可能會被違反。應變項為觀察受試者在20題選卡片作業中測試P和~Q的次數。結果發現，P機率小時，測試P卡片的次數顯著增加；當Q機率大時，測試~Q卡片的次數也增加，此結果支持Oaksford和Chater的最佳資料選擇理論。亦即，人的假設檢定歷程中含有歸納推理的歷程：將P和Q視為龐大母體的抽樣並評量抽樣的資訊大小。由於題目中提示規則可能會被違反時，~Q的測試數量顯著上升，顯示受試者是有證偽思考的能力，但通常不會主動使用。違規提示與P、Q機率大小之間完全沒有交互作用的現象顯示，以資訊增加量為主的思考與證偽的思考之間是獨立的，兩者皆會分別影響人的假設檢定行為。

While testing a hypothesis, people have difficulty in using falsifying evidence. Kirby’s signal detection theory（1994）assumes that people can falsify, but the probability of P and Q in a rule “if P then Q” would affect hypothesis-testing. He predicts that tending to falsify would increase if the probability of P is low. In contrast, Oaksford and Chater’s optimal data selection theory（1996）doesn’t assume that people can falsify, they predict that people would use whatever information that more expected information gain. In this study, the probability of P or Q in Wason’s selection task was manipulated and the Subject’s selection of P or ~Q card in 20 selection tasks were compared with-or-without rule violation hint. The results show that subjects select more P cards when probability of P is low, and more ~Q card when probability of Q is high. This pattern of result lend the optimal data selection theory, namely, the hypothesis-testing process involves a inductive reasoning process：P and ~Q are regarded as samples of a population and are evaluated according to expected information gain of testing the sample. Besides, the rule violation hint also increased ~Q selection significantly. It indicates that people can falsify, but do not use it automatically. The lack of interaction between rule violation hint and probability of P or Q suggests that the heuristic regarding information gain and the falsification logic may affect hypothesis-testing independently.