Drill 2 · Math · Statistics and Probability
SAT Math: Statistics and Probability (Drill 2) is a Math practice drill covering Statistics and Probability. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
SAT statistics and probability questions test weighted mean calculations, understanding how outliers affect measures of center and spread, computing probabilities of independent events, interpreting margin of error in survey results, and finding median from grouped data.
Question 1. Class A has 20 students with a mean score of 82. Class B has 30 students with a mean score of 90. What is the combined mean for all 50 students?
Explanation: Weighted mean = (20×82 + 30×90)/50 = 4,340/50 = 86.8. Not simply (82+90)/2 because class sizes differ.
Question 2. The data set {10, 20, 30, 40, 50} has a mean of 30. If 90 is added, what is the new mean?
Explanation: New sum = 150 + 90 = 240. New count = 6. Mean = 240/6 = 40.
Question 3. P(rain Saturday) = 0.4 and P(rain Sunday) = 0.3. If independent, what is P(rain both days)?
Explanation: For independent events: P(A and B) = 0.4 × 0.3 = 0.12.
Question 4. A poll of 500 voters found 62% support a policy, margin of error ±4%. Which is a plausible value for true support?
Explanation: Plausible range: 58%–66%. Only 65% falls within this interval.
Question 5. What is the median of {3, 7, 12, 18, 25, 30}?
Explanation: Even count: median = average of 3rd and 4th values = (12 + 18)/2 = 15.