STA 13 Lecture 7: Stat 13: lecture 7
Document Summary
P(f(e) = p(f and e) / p(e) P(e and f) = p(f/e) p(e) = p(e/f)p(f) F= get greater than or equal to 6. P(e and f ) = p(e)p(f) = ( )(4/6) = (cid:1151) If e1, e2, , e6 are all the different ways that event f can happen then. P(a or b) = p(a) + p(b) P(f) = p(e1, or e2, or , or e6) = sigma. Step 1: list all diferent ways the event of interest can happen. Step 2: find probabilities for all ways listed in step 1. Probability of 2 boys and 1 girl = (cid:489) + (cid:489) +(cid:489) = (cid:490) Ex2: box 4 green balls, 6 red balls. Step 1: list ways event (same color balls ) Both green (b1 = g and b2 =g) Both red ( b1 = r and b2 = r) P(b1 = g and b2 =g)= p(b1 = g)p(b2 =g) Pic (4/10)(3/9) + (6/10)(5/9) = 42/90 = 7/15.
