# Math425mid - Math 425(Fall 07 Midterm 2 November 7 2007...

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Math 425 (Fall ’07) Midterm 2 November 7, 2007 1 (10 pts) i) Give an example of a discrete random variable and one of a continuous random variable. ii) What is a random variable? iii) Describe (brieﬂy) the role of the mean and the variance. iv) What is the formula for the variance? v) Assume X is the binomial distribution with parameters n = 100 and p = 0 . 005. How do you suggest to compute P ( X 2)?

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2 (20 pts) For each of the random variables X below, determine the type of distribution which best models X. Give the values of the parameters of the distribution chosen. Give the reasons for your choice of the distribution and state your assumptions. i) A fair coin is tossed until head appears for the ﬁfth time. X = total number of tosses made. ii) There are 100 ﬁsh in a pond, 20 of which are carp. Suppose that 30 ﬁsh are caught. X = the number of carp. iii) There are 1 million participants in a nationwide lottery. Every participant has a 1/500,000 chance of winning a million-dollar grand prize. X = the number of winners of the grand
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## This note was uploaded on 04/24/2010 for the course MATH 425 taught by Professor K during the Spring '10 term at University of Michigan-Dearborn.

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Math425mid - Math 425(Fall 07 Midterm 2 November 7 2007...

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