GRE Subject Test: Math : Discrete Distributions

Study concepts, example questions & explanations for GRE Subject Test: Math

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Example Questions

Example Question #1 : Uniform Distribution

X is a continuously and uniformly distributed on the interval (0,50). Find the Expected Value (E[x]) and Variance (Var(x)) of X.

Possible Answers:

Correct answer:


Because x is a continuous uniform random variable the expected value and variance can be found with the following formulas:

X is uniform on (a,b). In this case a is 0 and b is 50. Plugging the values of a and b into the given formulas will give the answers:


Example Question #1 : Binomial Distribution

A fair coin is tossed 15 times. What is the probability of observing less than 3 heads?

Possible Answers:

Correct answer:


This problem uses the Binomial Distribution: 

For this problem n is the number of trials, or 15. Because the problem stated that the coin was a fair coin the probability of heads is one half, or .5.

The binomial distribution is a discrete distribution so the expression x<3 has to be broken down.

Adding the probabilities will give the final answer.

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