FAST Probability and Distributions 2

Question 1

A bag contains 4 red, 3 blue, and 5 green marbles. What is the probability of drawing a blue marble?

Accepted Answer

3/12

Answer

There are 3 blue marbles out of 4+3+5=12 total, so the probability is 3/12 = 1/4.

Question 2

Two fair dice are rolled. What is the probability of getting a sum of exactly 7?

Accepted Answer

1/6

Answer

There are 6 ways to get a sum of 7 out of 36 total outcomes, giving 6/36 = 1/6.

Question 3

If P(A) = 0.4 and P(B) = 0.5 and A and B are mutually exclusive, what is P(A or B)?

Accepted Answer

0.9

Answer

For mutually exclusive events, P(A or B) = P(A) + P(B) = 0.4 + 0.5 = 0.9.

Question 4

A normal distribution has mean 50 and standard deviation 10. Approximately what percentage of values fall between 40 and 60?

Accepted Answer

68%

Answer

Values within one standard deviation (40 to 60) of the mean cover approximately 68% of a normal distribution.

Question 5

A spinner has 8 equal sections numbered 1–8. What is the probability of landing on an even number?

Accepted Answer

1/2

Answer

Even numbers are 2,4,6,8 — that's 4 out of 8 sections, giving probability 4/8 = 1/2.

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