NSAA NSAA Mathematics - Statistics and Probability 1 — Questions and Answers
Question 1: A bag contains 4 red, 3 blue, and 5 green balls. What is the probability of drawing a blue ball?
- 1/4 (Correct answer)
- 1/3
- 1/5
- 1/6
Correct answer: 1/4
P(blue) = 3/(4+3+5) = 3/12 = 1/4.
Question 2: The mean of five numbers is 8. If four of the numbers are 6, 7, 9, and 10, what is the fifth number?
- 6
- 7
- 8 (Correct answer)
- 9
Correct answer: 8
Total sum = 5 × 8 = 40; sum of four = 32; fifth = 40 - 32 = 8.
Question 3: A die is rolled twice. What is the probability of getting a 6 on both rolls?
- 1/6
- 1/12
- 1/36 (Correct answer)
- 1/3
Correct answer: 1/36
P(6 on both) = 1/6 × 1/6 = 1/36 (independent events).
Question 4: The median of the data set {3, 7, 9, 2, 5} is:
- 5 (Correct answer)
- 7
- 9
- 3
Correct answer: 5
Sorted: {2, 3, 5, 7, 9}; middle value = 5.
Question 5: What is the variance of the set {2, 4, 6} given mean = 4?
- 2
- 4 (Correct answer)
- 8
- 16
Correct answer: 4
Using sample variance (n-1): [(2-4)²+(4-4)²+(6-4)²]/(3-1) = 8/2 = 4.
Question 6: If events A and B are mutually exclusive, what is P(A or B)?
- P(A) × P(B)
- P(A) + P(B) - P(A∩B)
- P(A) + P(B) (Correct answer)
- P(A) / P(B)
Correct answer: P(A) + P(B)
For mutually exclusive events, P(A∩B) = 0, so P(A or B) = P(A) + P(B).
NSAA NSAA Mathematics - Statistics and Probability 1
A bag contains 4 red, 3 blue, and 5 green balls.
What is the probability of drawing a blue ball?