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Using the standard rule for computing an expected value, how do you find the mean, μ, of a discrete random variable?
AMultiply each x by its probability and add the products
BMultiply every probability in the table together
CSubtract the smallest x value from the largest x value
DAdd every x value and divide by the count of x values
Answer & Solution
Correct answer: D. Add every x value and divide by the count of x values
1. A direct rule gives the expected value of a discrete random variable.
2. That rule is: multiply each x by its own P(x), then add all of those products together.
3. Option A states that rule exactly, so it is correct.
4. Option D describes an ordinary arithmetic mean of raw values with no weighting by probability, which is a different calculation.
_Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 4 "Discrete Random Variables", section 4.2 Mean or Expected Value and Standard Deviation_
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