PSYC 204 Lecture 9: PSYC STATS 9
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Marginal probability = p(x) of 1 single event. P(m) = probability of men (cid:2869)(cid:2870)(cid:2868)(cid:2870)(cid:2868)(cid:2868)=0. (cid:888) P(w) = probability of women (cid:2876)(cid:2868)(cid:2870)(cid:2868)(cid:2868)=0. (cid:886) Relative frequency = divide by n #number of students. P(a) = probability of arts student (cid:2877)(cid:2868)(cid:2870)(cid:2868)(cid:2868)=0. (cid:886)(cid:887) P(s) = probability of science student (cid:2869)(cid:2869)(cid:2868)(cid:2870)(cid:2868)(cid:2868)=0. (cid:887)(cid:887) Joint probability = probability of being simultaneously in 2+ categories. Conditional probability = probability of being something if have previous knowledge. P(b|a) = probability of obtaining b if already know a p(a|b) = probability of obtaining a if already know b. Use joint probability p(a b) marginal probability p(a) or p(b) Can calculate joint probability from conditional probability & vice-versa. *conditional probability = always divide by condition already know. P(b|a) = probability of obtaining b if already know a so (cid:4666)(cid:3003)(cid:1514)(cid:2885)(cid:4667) (cid:4666)(cid:2885)(cid:4667) P(b|a) = probability of obtaining a if already know b so (cid:4666)(cid:3002)(cid:1514)(cid:2886)(cid:4667) (cid:4666)(cid:2886)(cid:4667)
