Online Quiz 3

# Online Quiz 3 - Maple T.A. - Gradebook

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System Homepage » Class Homepage » Student Details » Student Assignment Details Stat 230 W09 : Gradebook Welcome Po-Wei Chuang [ My Profile ] Assignment detail for Po-Wei Chuang in Online Quiz 3: Po-Wei Chuang Login: pchuang Email: [email protected] Student ID: 20260696 Assignments completed: 22 Assignments active: 0 Question Grade 1 Let X be a random variable which takes on integer values, and suppose a and b are possible values of X. True or False: If P(X a) < P(X b) then a < b Your Answer: True Correct Answer: True Comment: This is True. If it wasn't, the only possibilities are: that a = b . Not possible since P(X a) < P(X b) 1. a > b. In this case then P(X a) = P(X b) + P(b < X a) P(X b) a contradiction. 2. Instructors Comment: 1.0 2 Let X represent a discrete random variable whose probability function is given by: f(x) = cx^3 for x=1,2,3,4,5; 0 otherwise What is the value of c? Your Answer: 1/225 Correct Answer: 1/225 Comment: To find c use the fact that the probabilities must add up to 1: c + 8c + 27c + 64c + 125c = 1, 225c = 1, c = 1/225 For E(X) we must sum xf(x) for all possible x: c + 16c + 81c + 256c + 625c = 979c = 4.3511 Instructors Comment: 1.0 3 In a uniform probability distribution for a discrete random variable X the probability function is given by:

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## This note was uploaded on 03/24/2010 for the course STAT 230 taught by Professor Various during the Winter '06 term at Waterloo.

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Online Quiz 3 - Maple T.A. - Gradebook

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