Interpreting Probability Correctly

Education · 10 questions

Probability calculations with the necessary assumptions stated in each question.

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1. A fair six-sided die is rolled once. What is the probability of rolling a 3?

   1. 1/2
   2. 1/5
   3. 1/6
   4. 1/3
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   C) 1/6

2. A bag contains 4 red and 6 blue balls. One ball is drawn at random. What is the probability it is red?

   1. 2/3
   2. 3/5
   3. 2/5
   4. 1/2
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   C) 2/5

3. Independent events A and B have P(A)=0.3 and P(B)=0.5. What is the probability that both occur?

   1. 0.8
   2. 0.035
   3. 0.15
   4. 0.2
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   C) 0.15

4. Two fair coins are tossed independently. What is the probability of at least one head?

   1. 3/4
   2. 1/4
   3. 1/3
   4. 1/2
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   A) 3/4

5. One card is drawn at random from a standard 52-card deck. What is the probability of drawing the ace of hearts?

   1. 1/52
   2. 1/4
   3. 1/13
   4. 4/52
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   A) 1/52

6. A Poisson process has a mean event rate of 2 per hour. What is the probability of no events in one hour?

   1. e⁻¹
   2. e⁻²
   3. 1 − e⁻²
   4. 2e⁻²
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   B) e⁻²

7. A test has 90% sensitivity, 95% specificity, and 1% disease prevalence. What is the chance a randomly selected person tests positive?

   1. 0.0095
   2. 0.0950
   3. 0.1000
   4. 0.0585
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   D) 0.0585

8. You randomly pick 1 of 3 doors hiding 1 car. The informed host always opens an unchosen goat door and offers a switch. Switching win probability?

   1. 1/3
   2. 2/3
   3. 3/4
   4. 1/2
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   B) 2/3

9. A fair die is rolled. A={2,4,6} and B={3,4,5,6}. Given that B occurred, what is the probability of A?

   1. 3/4
   2. 2/3
   3. 1/3
   4. 1/2
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   D) 1/2

10. A game awards €5 with probability 40% and €0 with probability 60%. What is the expected prize value?

    1. €2
    2. €3
    3. €1.50
    4. €0.60
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    A) €2