I am new to this field and subject. Please provide detailed answers that can help me learn the subject better. Show the expression you are using, and the substitutions you are making to calculate an answer.

Q1. 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

1. What are the "expected value" and "standard deviation" of X? Be sure to show your work? (If you are using Excel, please attach the spreadsheet).
2. If I were to compute the conventional mean of X, my answer would be x = 1.5. Why does the answer in (a) differ?