What Does ‘Probability’ Mean?
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,
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.
e.g. of a coin to come down heads or tails. Popper - statement.
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%)
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.
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.
Likely, possible, probable, chances are, maybe, perhaps, may/might, cat-in-hell's,
incredible, could be, you never know.
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)]