FAST Probability and Distributions 2 — Questions and Answers
Question 1: A bag contains 4 red, 3 blue, and 5 green marbles. What is the probability of drawing a blue marble?
- 1/4
- 1/3
- 3/12 (Correct answer)
- 1/5
Correct answer: 3/12
There are 3 blue marbles out of 4+3+5=12 total, so the probability is 3/12 = 1/4.
Question 2: Two fair dice are rolled. What is the probability of getting a sum of exactly 7?
- 1/6 (Correct answer)
- 7/36
- 1/7
- 6/36
Correct answer: 1/6
There are 6 ways to get a sum of 7 out of 36 total outcomes, giving 6/36 = 1/6.
Question 3: If P(A) = 0.4 and P(B) = 0.5 and A and B are mutually exclusive, what is P(A or B)?
- 0.2
- 0.9 (Correct answer)
- 0.1
- 0.45
Correct answer: 0.9
For mutually exclusive events, P(A or B) = P(A) + P(B) = 0.4 + 0.5 = 0.9.
Question 4: A normal distribution has mean 50 and standard deviation 10. Approximately what percentage of values fall between 40 and 60?
- 50%
- 95%
- 68% (Correct answer)
- 99.7%
Correct answer: 68%
Values within one standard deviation (40 to 60) of the mean cover approximately 68% of a normal distribution.
Question 5: A spinner has 8 equal sections numbered 1–8. What is the probability of landing on an even number?
- 3/8
- 1/2 (Correct answer)
- 5/8
- 1/4
Correct answer: 1/2
Even numbers are 2,4,6,8 — that's 4 out of 8 sections, giving probability 4/8 = 1/2.
Question 6: Which of the following describes a discrete probability distribution?
- Heights of adult males
- Time to complete a task
- Number of emails received per day (Correct answer)
- Temperature readings
Correct answer: Number of emails received per day
Number of emails is countable and takes only whole-number values, making it a discrete distribution.
Question 7: A card is drawn at random from a standard 52-card deck. What is the probability it is a face card (Jack, Queen, or King)?
- 1/13
- 3/52
- 3/13 (Correct answer)
- 1/4
Correct answer: 3/13
There are 12 face cards (3 per suit × 4 suits) out of 52, giving 12/52 = 3/13.
FAST Probability and Distributions 2
A bag contains 4 red, 3 blue, and 5 green marbles.
What is the probability of drawing a blue marble?