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MidtermSolutions

MidtermSolutions - Steven Weber Dept of ECE Drexel...

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Steven Weber Dept. of ECE Drexel University ENGR 361: Statistical Analysis of Engineering Systems (Spring, 2008) Midterm Exam Solutions (Wednesday, April 30) Instructions: There are three problems. Each is worth 10 points. You have 50 minutes to complete the exam. You are not to use any notes, books, or calculators. Partial credit is given for answers that are partially correct. No credit is given for answers that are wrong or illegible. Write neatly. Name: Student ID #: Signature: Problem 1: Problem 2: Problem 3: Total: www.ece.drexel.edu/faculty/sweber 1 April 30, 2008

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Steven Weber Dept. of ECE Drexel University Name: Student ID #: Score: Problem 1 (10 points) A gumball machine contains 100 gumballs, colored red, blue, and green. There are 27 red, 43 blue, and 30 green gumballs. Inserting a coin into the gumball machine yields a gumball. Each gumball is equally likely to be selected for each inserted coin. 1. (2 points) What is the probability that of getting 3 red gumballs, 2 blue gumballs, and 5 green gumballs after inserting the first 10 coins? ( 27 3 )( 43 2 )( 30 5 ) ( 100 10 ) . (1) 2. (2 points) What is the probability of not having a red gumball after inserting the first 10 coins? ( 73 10 ) ( 100 10 ) . (2) 3. (2 points) What is the probability of having exactly two colors of gumballs after inserting the first 10 coins? ( 43+30 10 ) + ( 27+43 10 ) + ( 27+30 10 ) - ( 27 10 ) - ( 43 10 ) - ( 30 10 ) ( 100 10 ) . (3) 4. (1 point) The person ahead of you inserts the first coin into the gumball machine and takes a gumball. She gets a red gumball. What is the probability that you get a green gumball?
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