Re:Controversial Facts In Mathematics
by rskar on Wednesday March 27, 2013 @02:45PM
(#5451226)
Nope, take a closer look, Event B is pictured like a crescent moon, labelled "People who are accountants and not plumbers", and described thus: "There's also the probability 'B' that the guy who fixed my water heater is only an accountant and not a plumber." Plumber status within B is clearly "Not a plumber".
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Re:Controversial Facts In Mathematics
by hackinthebochs on Wednesday March 27, 2013 @06:05PM
(#5452299)
You're certainly right about the details you mentioned. But they are not relevant to the problem. "Accountant and not a plumber" was not in the question at all. Lets make it more precise. X = is accountant, Y = is plumber. The question is which is greater: P(X) or P(X and Y). It should be clear that the event "X and Y" is completely contained within the event "X". To put it another way, P(X) = P(X and Y) + P(X and ~Y) (we are summing over all possible unconstrained events, in this case Y and ~Y). Hence, P(X) >= P(X and Y)