Week 2 - Judgement & Probability

Week 2 - Judgement & Probability - Week 2 Mind...

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What Does ‘Probability’ Mean? Logical possibility . Mostly applies to true games of chance, e.g. probability of drawing an ace from a fair deck is 4 in 52, or .077 (7.7%) Decks of cards, coins, etc Frequency As proportion of possible occurrences; natural sampling. Number of times something happens as a proportion of times it could have happened. Degree of belief Subjective judgement of the probability of an event. Probablity you think there is of it happening. Propensity e.g. of a coin to come down heads or tails. Popper - statement. Logical possibility Expressed as a number between 0 (certain not to occur) and 1 (certain to occur) or a percentage or as odds. Mostly applis to true games of chance, e.g. probability of drawing an ace from a fair deck is 4 in 52, or 0.077 (7.7%) Frequency As a proportion of possible occurences (the 'collective') e.g chances of dying in a car vs. air crash, chances of being harmed by a vaccine, number of winners out of a total number of lottery players. Natural Sampling simple 'counts' of numbers of occurences, e.g. number of dogs vs. cats in an area; number of bad driving incidents caused by BMW drivers/ people who wear hats; Sept 09 news item: why are there so many spiders this year? Degree of Belief Subjective assessment of likelihood of unique events, e.g. chance of Second Coming, meeting Mr/Mrs right, climate catastrophe, who killed JFK, Elvis still alive, the Loch Ness Monster. Verbal Probability Likely, possible, probable, chances are, maybe, perhaps, may/might, cat-in-hell's, incredible, could be, you never know. .. Bayesian theory Bayes’ rule enables you to work out precisely how beliefs (H) change in response to information, or data (D). Estimating your degree of belief and the likelihood of the new information [p(D)]
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Week 2 - Judgement & Probability - Week 2 Mind...

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