# POL101Y1 Lecture Notes - Conditional Probability, Random Variable

## Document Summary

Cannot study everyone in population so must take a sample (random). Random sample, define probability of observing certain characteristics. Repeated sampling from the same population ie. * rolling the die example* Probability is= proportion of times you can observe a characteristics from repeated sampling from the same population (long run relative frequency) 1 bucket and 3 different plastic ducks (after the model of canadian voters) A girl is drawing a duck from the basket, and she wants the princess duck. 1/(1+1+1)=1/3 * # desired duck (numerator)/ # ducks in total. =0. 3333 or 33. 33% now 2 yellow duckies, 1 purple, 1 princess. The probability of observing a certain characteristic equals the proportion of individuals in the population who have voted for the conservatives. We can compute this because we know the population distribution. In real life we do not know the actual distribution of the population. Therefore we need to make inference based on random sample.