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Probability and Distributions Flashcards

7 cards from real FAST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Probability and Distributions flashcards as text

  1. A survey shows that 70% of students pass a test on their first try. In a class of 20 students, what is the expected number who pass?

    Answer: 14

    Expected passes = n × p = 20 × 0.70 = 14.

  2. What is the complement of the event 'rolling at least a 3' on a single fair die?

    Answer: Rolling a 1 or 2

    The complement of 'at least 3' (outcomes 3,4,5,6) is 'less than 3' (outcomes 1 and 2).

  3. A probability distribution has values X = {1, 2, 3} with P(1)=0.2, P(2)=0.5, P(3)=0.3. What is E(X)?

    Answer: 2.1

    E(X) = 1(0.2) + 2(0.5) + 3(0.3) = 0.2 + 1.0 + 0.9 = 2.1.

  4. Which of the following best describes a negatively skewed distribution?

    Answer: The tail extends to the left

    A negatively (left) skewed distribution has a tail that stretches toward lower values on the left.

  5. A jar holds 5 red and 5 blue chips. Two chips are drawn WITHOUT replacement. What is the probability both are red?

    Answer: 2/9

    P(both red) = (5/10) × (4/9) = 20/90 = 2/9.

  6. A data set has mean 80 and standard deviation 5. A score of 90 has a z-score of:

    Answer: 2

    Z = (90 − 80) / 5 = 10 / 5 = 2.

  7. If P(A) = 0.5, P(B) = 0.4, and P(A and B) = 0.2, what is P(A or B)?

    Answer: 0.7

    P(A or B) = P(A) + P(B) − P(A and B) = 0.5 + 0.4 − 0.2 = 0.7.