650-Q8

Let X represents the number of times a student visits a nearby pizza shop in one month period. Assume that the following table is the probability distribution of X:

X P(X)

0 0.10

1 0.30

2 0.40

3 0.20

a.What are the "expected value" and "standard deviation" of X?Use Excel and a step-by-step guide spreadsheet or formula.

b.If I were to compute the conventional mean of X, my answer would be = 1.5. Why does the answer in (a) differ?