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Probability and Statistics Concepts Flashcards

7 cards from real GRE 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 Statistics Concepts flashcards as text

  1. A fair six-sided die is rolled twice. What is the probability that the sum of the two rolls equals 7?

    Answer: 1/6

    There are 6 ordered pairs summing to 7 out of 36 equally likely outcomes, giving 6/36 = 1/6.

  2. If events A and B are independent with P(A) = 0.4 and P(B) = 0.5, what is P(A and B)?

    Answer: 0.2

    For independent events the joint probability is the product, 0.4 × 0.5 = 0.2.

  3. The mean of the data set {4, 8, 8, 10, 15} is closest to which value?

    Answer: 9

    The sum is 45 and there are 5 values, so the mean is 45/5 = 9.

  4. A bag has 3 red and 2 blue marbles. Two are drawn without replacement. What is the probability both are red?

    Answer: 3/10

    P = (3/5) × (2/4) = 6/20 = 3/10.

  5. What is the median of the set {12, 3, 7, 9, 15, 6}?

    Answer: 8

    Sorted, the middle two values are 7 and 9, so the median is (7+9)/2 = 8.

  6. In a standard normal distribution, approximately what percent of values fall within one standard deviation of the mean?

    Answer: 68%

    The empirical rule states about 68% of data lies within one standard deviation of the mean.

  7. If P(A) = 0.7, what is the probability that A does NOT occur?

    Answer: 0.3

    The complement is 1 − 0.7 = 0.3.