A discrete random variable X takes the values 1, 2, and 4 with probabilities 0.2, 0.5, and 0.3, respectively. What is E(X)?
Correct answer: B. 2.40
- A. 2.10
- B. 2.40
- C. 2.70
- D. 3.00
Explanation
The expected value is found by multiplying each value by its probability and adding the results: (1 × 0.2) + (2 × 0.5) + (4 × 0.3) = 2.4. It is a probability-weighted average, not the simple average of the values.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
About Probability and Probability Distributions
Probability covers sample spaces, events, complements, mutually exclusive and independent events, conditional probability, addition and multiplication rules, and tree diagrams. Distributions describe discrete random variables through probability tables, expected value and variance, including binomial and normal models where their conditions and parameters must be identified.
Practise Probability and Probability Distributions
30 free Probability and Probability Distributions MCQs from Quantitative Methods, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Quantitative Methods questions like this
Quantitative Methods is on this paper prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for it.
More Probability and Probability Distributions questions
For a Poisson distribution with parameter λ = 4, what is the variance of the distribution?
If X follows a binomial distribution with n = 20 and probability of success p = 0.3, what is its expected value?
A fair coin is tossed four times. What is the probability of getting exactly two heads?
A trial has a 0.2 probability of success on each independent attempt. What is the probability that the first success occurs on the third attempt?
If X has a standard normal distribution, what is P(X > 0)?
If two events A and B are independent, with P(A) = 0.6 and P(B) = 0.5, what is P(A ∩ B)?