Patients who have artificial hip-replacement surgery experience pain the first day after surgery.

Typically, the pain is measured on a subjective scale using values of 1 to 5. Let x represent the random variable, the pain score as determined by the patient.

The probability distribution for x is believed to be:

a. Find the mean of x.

b. Find the standard deviation of x.

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X 1 2 3 4 5 P(x) 0.10 0.15 0.25 0.35 0.15