CLAST Statistics and Probability 4 — Questions and Answers
Question 1: A survey of 200 students found 120 prefer math. Based on this sample, what is the estimated probability that a randomly selected student prefers math?
- 0.4
- 0.5
- 0.6 (Correct answer)
- 0.7
Correct answer: 0.6
Experimental probability = 120/200 = 0.6.
Question 2: The data set 10, 15, 15, 20, 25, 100 has a mean of 30.8. Which measure best represents the center of this data?
- Mean
- Mode
- Median (Correct answer)
- Range
Correct answer: Median
The outlier 100 inflates the mean, so the median (17.5) better represents the typical value.
Question 3: A jar contains 4 red and 6 white balls. Two balls are drawn without replacement. What is the probability both are red?
- 2/15 (Correct answer)
- 4/25
- 1/6
- 2/5
Correct answer: 2/15
P(both red) = (4/10) × (3/9) = 12/90 = 2/15.
Question 4: A line graph shows a company's revenue increasing from $2M in 2020 to $5M in 2023. What is the average annual increase?
- $1M (Correct answer)
- $0.75M
- $1.5M
- $3M
Correct answer: $1M
Total increase = $3M over 3 years, so average annual increase = $3M/3 = $1M per year.
Question 5: A die is rolled once. What is the probability of rolling a prime number?
- 1/3
- 1/2 (Correct answer)
- 2/3
- 1/6
Correct answer: 1/2
Prime numbers on a die are 2, 3, and 5 — that is 3 out of 6 faces, so P = 3/6 = 1/2.
Question 6: A histogram shows test scores: 50–60 (5 students), 60–70 (12 students), 70–80 (18 students), 80–90 (10 students). What percent scored in the 70–80 range?
- 40%
- 44%
- 36% (Correct answer)
- 38%
Correct answer: 36%
Total students = 45; 70–80 range has 18, so percent = 18/45 × 100 = 40%.
Question 7: If events A and B are independent, P(A) = 0.5, and P(B) = 0.4, what is P(A and B)?
- 0.9
- 0.1
- 0.2 (Correct answer)
- 0.45
Correct answer: 0.2
For independent events, P(A and B) = P(A) × P(B) = 0.5 × 0.4 = 0.2.
CLAST Statistics and Probability 4
A survey of 200 students found 120 prefer math.
Based on this sample, what is the estimated probability that a randomly selected student prefers math?