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Questions › DSE › DSE 2005 › Q23
2 marks, −1Statistics › Random variables and standard distributions › Geometric and hypergeometric distributionsHardabout 3 min

DSE 2005 Question 23: Random variables and standard distributions

A random variable has outcomes Success and Failure with probabilities 3/43/43/4 and 1/41/41/4 respectively. A gambler observes the sequence of outcomes of this variable and receives a prize of 2n2^n2n if nnn is the first time that Success occurs. What is the expected value of the gambler's prize?

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Plain-text version

A random variable has outcomes Success and Failure with probabilities 3/4 and 1/4 respectively. A gambler observes the sequence of outcomes of this variable and receives a prize of 2ⁿ if n is the first time that Success occurs. What is the expected value of the gambler's prize? (A) 1 (B) 2 (C) 3 (D) 4

Also written as: A random variable has outcomes Success and Failure with probabilities 3/4 and 1/4 respectively. A gambler observes the sequence of outcomes of this variable and receives a prize of 2^n if n is the first time that Success occurs. What is the expected value of the gambler's prize?

Random variables and standard distributions has come up 173 times in 7 exams since 2005.

What this question tests

This question is on Geometric and hypergeometric distributions, part of Random variables and standard distributions in Statistics.

Waiting for a first success, and successes in draws without replacement.

TestStop has 7 past-paper questions on this subtopic.

Practise Random variables and standard distributionsMore on Geometric and hypergeometric distributions

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Question from the DSE 2005 paper. Solutions are TestStop's own. Not affiliated with or endorsed by any examination authority.