School Improvement in Maryland
Sample Item Scoring Information Return

Standard 5.0 Knowledge of Probability

Topic B. Theoretical Probability

Indicator 1. Determine the probability of one simple event comprised of equally likely outcomes

Objective b. Express the probability of an event as a decimal

Selected Response (SR) Item

Allison plays baseball. In the last 25 times at bat she made a hit 4 times. Based on her last 25 at bats, what is the experimental probability that Allison will make a hit on her next time at bat?

  1. 0.04
  2. 0.16
  3. 0.25
  4. 0.40

Correct Answer
B. 0.16

Answer Annotation

  1. 0.04    (4 times at bat)
  2. 0.16    (correct answer)
  3. 0.25    (25 times at bat)
  4. 0.40    (40 %)

Answer B: Based on the number of hits 4 out of the number of times at bat 25, the experimental probability she will make a hit on her next at bat is 4/25 = 0.16
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