chpater 8 cont - 10/19/2011 1 Logic and reasoning [15] 19...

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Unformatted text preview: 10/19/2011 1 Logic and reasoning [15] 19 Oct rest of Chapter 8 Inductive reasoning Two kinds of arguments- Deductive- Inductive- Deductive: conclusion follows 100%- Inductive: less than 100% Three types of inductive arguments- Enumerative induction (parts b whole)- Analogical induction (X :: Y b A :: B)- Causal induction / reasoning (shared causal properties) Enumerative Induction: An inductive argument pattern in which we reason from premises about individual members of a group to conclusions about the group as a whole . X % of the observed members of group A have property P. Therefore, X % of all members of group A probably have property P. General pattern Target group (or target population)In enumerative induction, the whole collection of individuals under study. Sample (or sample member)In enumerative induction, the observed members of the target group. Relevant property (or property in question)In enumerative induction, a property, or characteristic, that is of interest in the target group. Two issues with the sample- Too small- Not representative 10/19/2011 2 Hasty generalization The fallacy of drawing a conclusion about a target group based on an inadequate sample size. Biased sample A sample that does not properly represent the target group. Representative sample In enumerative induction, a sample that resembles the target group in all relevant ways. Recap Hasty generalization The fallacy of drawing a conclusion about a target group based on an inadequate sample size. Biased sample A sample that does not properly represent the target group. Representative sample In enumerative induction, a sample that resembles the target group in all relevant ways. Recap Random sample A sample that is selected randomly from a target population in such a way as to ensure that the sample is representative. In a simple random selection, every member of the population has an equal chance of being selected for the sample. The motel example:- The sample wasnt random- The front people are chosen to be nice, so the selection of whom we met is not random- Weak argument: not because of the sample size, but because of bias Recap When enumerative induction matters a lot:- Drug testing Target population (Tp): all people suffering of a certain disease Sample (S): volunteers (among those suffering) Property (P): getting cured / adverse effects The bigger the sample, the better The more representative sample, the better = the more random (= diverse), the better Volunteering problem The longer the testing, the better When enumerative induction matters a lot:- Opinion polling Target population (Tp): all voters Sample (S): people chosen by the pollsters Property (P): voting a certain way / candidate The bigger the sample, the better The more representative sample, the better = the more random (= diverse), the better Polling problems Opinion polls- Key-question: do they generate accurate data?Key-question: do they generate accurate data?...
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chpater 8 cont - 10/19/2011 1 Logic and reasoning [15] 19...

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