Quiz III- Sol

# Quiz III- Sol - QUIZ III- BIT 2405- Solutions Problems 1-3...

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QUIZ III- BIT 2405- Solutions Problems 1-3 The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. 1. What is the probability that a player weighs more than 241.25 pounds? 1) 0.0495 2) 0.0567 3) 0.0674 4) 0.0002 2. What is the probability of a player weighing less than 250 pounds? 1) 0.0228 2) 0.9772 3) 0.0500 4) 0.9500 3. What percent of players weigh between 180 and 220 pounds? 1) 0.0577 2) 0.5762 3) 0.0675 4) 0.6752 4. The life expectancy of a particular brand of tire is normally distributed with a mean of 40,000 and a standard deviation of 5,000 miles. What percentage of tires will have a life of 36,000 to 46,000 miles? 1) .7698 2) .8967 3) .6897 4) None of the above (.663) 5. The grade point averages of a large population of college students are approximately normally distributed with a mean of 2.4 and a standard deviation of 0.8. What is the probability that a randomly selected student will have a grade point average in excess of 3.0? 1) .1133 2) .2266 3) .7734 4) None of the above P(X>3)=P(Z>.75)=1-P(Z<.75)=1-.7734=.2266 6. The length of time required to complete a college achievement test is found to be normally distributed with a mean of 70 minutes and a standard deviation of 12 minutes. When should the test be terminated if we wish to allow sufficient time for 90% of the students to complete the test? 1) After 98.76 minutes 2) After 85.36 minutes 3) After 76.34 minutes 4) None of the above P(Z<z)=.9 z=1.28=(X-70)/12 X=85.36

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7. Suppose we toss a coin 25 times. What is the probability that we get at least 10 but not more than 15 heads? 1) .7698 2) .8967 3) .2302 4) None of the above Using normal approximation to binomial distribution P(9.5 X 15.5)=P(X 15.5)-P(X 9.5)=P(Z 1.2)-P(Z -1.2)=.8849-.1151=.7698 8. A new treatment for baldness is known to be effective in 70% of the cases treated. A random sample of 50 men were chosen and treated. What is the probability that the treatment was effective in at least 38 men? 1) .3206 2) .7794 3) .2602 4) None of the above (.2206) Problems 9-12 Find the following probabilities using the standard normal distribution: 9. P(z > -2.13) 1) .8943 2) .9834 3) .0166 4) None of the above 10. P(z < -0.15) 1) .5596 2) .2202 3) .4404 4) None of the above 11. P(-1.38 < z < 2.07) 1) .1030 2) .2202 3) .8970 4) None of the above 12. P( 0.12 < z < 2.90) 1) .5497 2) .4503 3) .8970 4) None of the above Problems 13-14 Using the standard normal distribution: 13. Find the value of z such that P(Z>z) = 0.7967 1) .83 2) -.83 3) -.38 4) None of the above
14. Find the value of z such that P(Z<z) = 0.063 1) 1.53 2) -1.53 3) -.53 4) None of the above Problems 15-16 Students of Virginia Tech spend an average of \$5 a day on lunch. The standard deviation of the expenditure is

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## This note was uploaded on 04/20/2009 for the course BIT 2405 taught by Professor Plkitchin during the Fall '08 term at Virginia Tech.

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Quiz III- Sol - QUIZ III- BIT 2405- Solutions Problems 1-3...

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