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1.

A bag has 4 red and 6 blue balls. One ball is drawn at random. The probability that it is red is:

2/5

3/5

4/6

1/4

2.

In a group of 40 students, 25 play football, 18 play basketball and 10 play both. The probability that a football player also plays basketball is:

10/18

18/40

2/5

1/2

3.

For two events with P(A) = 0.3, P(B) = 0.5 and P(A ∩ B) = 0.15, which statement is true?

A and B are not independent, since P(A ∩ B) is less than P(B)

A and B are independent, since P(A ∩ B) = P(A) × P(B)

A and B are independent, since P(A) is less than P(B)

A and B are not independent, since P(A) + P(B) ≠ 1

4.

Two fair coins are tossed and X is the number of heads. The expected value E(X) is:

0.5

1.5

2

1

5.

For the same random variable X (the number of heads in two coin tosses), the variance Var(X) is:

0.5

0.25

1

1.5

6.

A fair coin is tossed 4 times. The probability of exactly 2 heads is:

1/4

1/2

3/8

5/16

Statistics, Conditional Probability and Random Variables — Lesson quiz