CLAST Statistics and Probability 3 — Questions and Answers
Question 1: A stem-and-leaf plot shows stems 2, 3, 4 with leaves 2|1 5, 3|0 3 8, 4|2. What is the range of the data set?
- 21 (Correct answer)
- 20
- 22
- 19
Correct answer: 21
The maximum value is 42 and the minimum is 21, so the range = 42 − 21 = 21.
Question 2: Events A and B are mutually exclusive. P(A) = 0.4 and P(B) = 0.25. What is P(A or B)?
- 0.1
- 0.65 (Correct answer)
- 0.55
- 0.75
Correct answer: 0.65
For mutually exclusive events, P(A or B) = P(A) + P(B) = 0.4 + 0.25 = 0.65.
Question 3: A frequency table shows: Score 70 (freq 4), 80 (freq 6), 90 (freq 2). What is the mean score?
- 78.3 (Correct answer)
- 80
- 79.2
- 76.7
Correct answer: 78.3
Mean = (70×4 + 80×6 + 90×2) / (4+6+2) = (280+480+180)/12 = 940/12 ≈ 78.3.
Question 4: Which type of graph is BEST suited to display how a quantity changes over time?
- Pie chart
- Bar graph
- Line graph (Correct answer)
- Histogram
Correct answer: Line graph
Line graphs are specifically designed to show trends and changes in data over time.
Question 5: Two fair coins are flipped. What is the probability of getting exactly one head?
- 1/4
- 3/4
- 1/2 (Correct answer)
- 1/3
Correct answer: 1/2
The sample space is {HH, HT, TH, TT}; exactly one head occurs in 2 of 4 outcomes, so P = 2/4 = 1/2.
Question 6: A data set has a mean of 50 and a standard deviation of 5. A score of 60 is how many standard deviations above the mean?
- 1
- 2 (Correct answer)
- 5
- 10
Correct answer: 2
z = (60 − 50) / 5 = 10/5 = 2 standard deviations above the mean.
Question 7: In a box-and-whisker plot, what does the box itself represent?
- The range of all data
- The interquartile range (IQR) (Correct answer)
- The mean and median
- The standard deviation
Correct answer: The interquartile range (IQR)
The box spans from the first quartile (Q1) to the third quartile (Q3), representing the interquartile range.
CLAST Statistics and Probability 3
A stem-and-leaf plot shows stems 2, 3, 4 with leaves 2|1 5, 3|0 3 8, 4|2.
What is the range of the data set?