Assume that Xi ’s are independent of each other and independent of N. Further assume that they have same P mean and variance i.e., E[Xi ] = k, Var(Xi ) = m. Let Y be the stores total sales i.e., Y = sigmai Xi . Find E[Y ] and Var(Y ).
Continuous Probability Distributions
Probability distributions are of two types, which are continuous probability distributions and discrete probability distributions. A continuous probability distribution contains an infinite number of values. For example, if time is infinite: you could count from 0 to a trillion seconds, billion seconds, so on indefinitely. A discrete probability distribution consists of only a countable set of possible values.
Normal Distribution
Suppose we had to design a bathroom weighing scale, how would we decide what should be the range of the weighing machine? Would we take the highest recorded human weight in history and use that as the upper limit for our weighing scale? This may not be a great idea as the sensitivity of the scale would get reduced if the range is too large. At the same time, if we keep the upper limit too low, it may not be usable for a large percentage of the population!
Let N be the number of customers that visits a certain shop in a given day. Suppose that E[N ] = e, and Var(N ) = v. Let Xi be the amount that the i th customer spends on average. Assume that Xi ’s are independent of each other and independent of N. Further assume that they have same P mean and variance i.e., E[Xi ] = k, Var(Xi ) = m. Let Y be the stores total sales i.e., Y = sigmai Xi . Find E[Y ] and Var(Y ).
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