Which of the following statements are true for discrete random variables? Explain why each statement is true or false.
a. The mean can be negative.
b. The mean can be zero.
c. The standard deviation can be negative.
d. The standard deviation can be zero.
e. The standard deviation can be greater than the mean.
f. The variance can be negative.
g. The variance can be zero.
h. The expected value of X2 is always positive.
i. The expected value of X2 is always smaller than the square of the mean