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SampleMidterm1ExamStat3345

# SampleMidterm1ExamStat3345 - STAT 3345 PROBABILITY MODELS...

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STAT 3345 – PROBABILITY MODELS FOR ENGINEERS SPRING 2010 SAMPLE MIDTERM 1 EXAM Problem 1 A university librarian produced the following probability distribution of the number of times a student walks into the library over the period of a semester. x 0 5 10 15 20 25 30 40 50 75 100 p ( x ) .22 .29 .12 .09 .08 .05 .04 .04 .03 .03 .01 (a) Calculate the mean of X . (b) Calculate the standard deviation of X . Problem 2 The following data represent the birth weights (in grams) of babies born in 2002 along with the period of gestation. Birth Weight Period of Gestation (in grams) Preterm Term Postterm Total Less than 1000 28,247 202 32 28,481 1000-1999 78,532 10,325 1,051 89,908 2000-2999 228,064 606,046 39,481 873,591 3000-3999 135,790 2,293,927 192,566 2,622,283 4000-5000 8,974 315,821 34,319 359,114 Over 5000 211 4,524 556 5,291 Total 479,818 3,230,845 268,005 3,978,668 (a) What is the probability that a randomly selected baby born in 2002 was preterm? (b) What is the probability that a randomly selected baby born in 2002 weighted less than 3000 grams? 1

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(c) What is the probability that a randomly selected baby born in 2002 weighted less than 3000 grams or was preterm? (d) Are the event the baby born in 2002 weighted less than 3000 grams and the event the baby was preterm independent?
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SampleMidterm1ExamStat3345 - STAT 3345 PROBABILITY MODELS...

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