17. Of the automobiles produced at a particular plant, 40% had a certain defect. Suppose a company purchases five of these cars. What is the expected value of the number of cars with defects? 18. The life expectancy of a particular brand of lightbulb is normally distributed with mean of 1500 hours and a standard deviation of 75 hours. (a) What is the probability that a lightbulb will last less than 1410 hours? (b) What is the probability that a lightbulb will last between 1416 and 1450 hours? (c) What is the probability that a lightbulb will last between 1563 and 1648 hours? 19. A packing machine is set to fill a cardboard box with a mean average of 16.1 ounces of cereal. Suppose the amounts per box form a normal distribution with a standard deviation of 0.04 ounces. (a) Ten percent of the boxes will contain more than what number of ounces? (b) Eighty percent of the boxes will contain more than what number of ounces? (c) What percentage of the boxes will end up with at least 1 pound of cereal? (d) The middle 90% of the boxes will be between what two weights? 20. One- thousand students at a city high school were classified according to both GPA and whether or not they consistently skipped school. GPA <2.0 2.0-3.0 >3.0 Many skipped school 80 25 5 Few skipped school 175 450 265 (a) What is the probability that a student has a GPA between 2.0 and 3.0? (b) What is the probability that a student has a GPA under 2.0 and has skipped many classes? (c)What is the probability that a student has a GPA under 2.0 or has skipped many classes? (d) What is the probability that a student has a GPA under 2.0 given that he has skipped many classes? (e) Are events “GPA between 2.0 and 3.0” and “skipped many classes” independent events? Explain. 21. When describing a graphical display, if the shape is approximately symmetric, you should use _________ as a measure of center and _______ as a measure of spread. If the shape is skewed, you should use _______ as a measure of center and ________ as a measure of spread.
22. Mathematically speaking, casinos and life insurance companies make a profit because: (A) Of their understanding of sampling error and source of bias. (B) Of their use of well-designed, well-conducted surveys and experiments. (C) Of their use of simulation of probability distributions. (D) Of the law of large numbers. 23. A club sells raffle tickets and there are 10 prizes at $25 and one prize of $100. If 200 tickets are sold, what do you expect to win if you bought one ticket? If the ticket cost $5, do you expect to lose or gain? Explain 24. The probability model below describes the number of repair calls than an appliance repair shop may receive during an hour. Repair Calls 0 1 2 3 Probability 0.1 0.3 0.4 0.2
- Summer '16