Exam_1_Eng_Prob_Spring_2011

# Exam_1_Eng_Prob_Spring_2011 - 3/25/2011 Exam 1 (Eng Prob...

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To pr int higher -r esolution math symbols, click the Hi-Res Fonts for Printing button on the jsMath control panel. ECSE-2500 Engineering Probability, Exam 1, March 1, 2011 NAME: _____ answers EMAIL:___________________________ RIN:______________ Answer every question. There are four pages with four questions, total 68 points. You may write free for any 6 points. We implemented this by adding 6 points to everyone and capping the total at 68. This exam is closed book but a calculator and one 2-sided letter-paper-size note sheet are allowed. You may not use other computers or communication devices, or share material with other students. 1. In the following questions, the life of a light is an integer number of weeks, not a real number. I.e., these distributions are discrete not continuous. You have a stockroom of 2000 hi quality and 1000 lo quality light bulbs. Unfortunately they are unlabeled. You take one light, but don't know which it is. H is the event that it's a hi quality light. The probability that a hi quality light dies after k whole weeks (i.e., in the k+1-st week) is geometric. The probability that it dies after 0 whole weeks is 0.1. For a lo quality light, that probability is 0.2. a. [2 pts] What's the mean number of weeks that a hi quality light will work? Prob of dying after exactly k whole weeks: p 1 (1 ) 1) p Reasonably close, i.e., off-by-1, errors are allowed. b. [2] What's the probability that the light that you took was hi quality? 2000/(2000+1000) = 2/3 c. [4] What's the mean life of the unknown light that you took?

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## This note was uploaded on 11/29/2011 for the course ECSE 2500 taught by Professor Radke during the Spring '11 term at Rensselaer Polytechnic Institute.

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Exam_1_Eng_Prob_Spring_2011 - 3/25/2011 Exam 1 (Eng Prob...

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