MATH 11 Lecture Notes - Lecture 9: Random Variable, Weighted Arithmetic Mean, Standard Deviation
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At the dmv, a teller is either in a good or bad mood. In the rare event of a good mood (10%) of the time, you are served 2 minutes. During a bad mood, the same transaction takes 8 minutes. We don"t say 5 minutes (the average of 2 and 8) because the values 2 and 8 are not equally likely. We need a weighted average to find our expected wait time: A random variable is a variable that takes on the possible numeric values that result from a random event. A discrete random variable has only finitely-many outcomes (ex: let x be the dmv time from last slide) or space between the values (ex let y be the number of meteors that have hit a planet). A probability model lists the different outcomes for a random variable and gives the probability of each outcome. Let x be your processing time at the dmv.
