# Biology 2244A/B Lecture Notes - Lecture 5: Sample Space, Mammography, Hulu

## Document Summary

C: flip no heads (complement of b) E: flip heads or tails on first flip. A random outcome is one that is uncertain but has a regular distribution in a large # of repetitions. The probability of a random outcome is the proportion of times the outcome would occur in a very long series of repetitions. Relates to law of large #s (p. 94) As more tosses carry on, the proportion will go closer and closer to the probability (0. 5 in this case) Suppose a family plans to have 3 kids. Assuming single births and equal chances of boy/girl, find the prob that the first child will be a girl or the 2nd child will be a girl. Sample space = {ggg, ggb, gbb, bbb, bbg, bgg, bgb, gbg} A = {ggg, ggb, gbb, gbg} b = {ggg, ggb, bgg, bgb} A or b = {ggg, ggb, gbb, } P(a or b) = p(a) + p(b) - p(a and b)