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Case analysis is one of the most general and applicable methods of analytical thinking, depending only on the division of a problem, decision or situation into a sufficient number of separate cases. Analysing each such case individually may be enough to resolve the initial question. The principle of case analysis is invoked in the celebrated remark of Sherlock Holmes, to the effect that when one has eliminated the impossible, what remains must be true, however unlikely it seems. The logical roots of the Holmes remark speak to the principle of excluded middle. That indicates the importance to case analysis of logical disjunction: stringing together propositions with the logical connective ''"or"''. Medical diagnosis can indeed follow the Holmes pattern, with a patient's symptom possibly caused by a number of conditions: the patient suffers from ''A'' or ''B'' or ... or illness ''I''; see differential diagnosis. Deductive logic is applied to reducing the number of cases; see case-based reasoning. A canonical statement of case analysis in the sentential calculus is this: "If a statement ''P'' implies a statement ''Q'', and a statement ''R'' also implies ''Q'', and at least one of ''P'' or ''R'' is true, then ''Q'' must be true." : ==Exhaustive analysis== The most important issue in this style of case analysis is that the cases should be collectively ''exhaustive'': everything is covered. The condition that they should be ''exclusive'', while convenient, is not to be assumed lightly; for example a patient's liver problem might be caused by hepatitis ''and'' abuse of alcohol, with one factor not ruling out the other. This points up the distinction between exclusive or, and logical disjunction which is the default meaning of 'or' (in logic, mathematics and science) and which is non-exclusive. Case analysis of the non-overlapping kind is a special case, only. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Case analysis」の詳細全文を読む スポンサード リンク
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