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Quiz 1 Sp10

# Quiz 1 Sp10 - No long calculation necessary but explain...

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Quiz 1 Statistics 21 Spring 2010 Ibser 1. A large class takes a test, and the table shows their scores. For all parts of this problem, assume that the scores are continuous and that they are evenly distributed within each separate class interval. The maximum score is 100 and you should use that as the right endpoint of the rightmost bar. Use the minimum score, 10, as the left endpoint of the leftmost bar. The data is in terms of percentiles, so think about how to convert it into the usual form of class intervals and the percent in each interval. Percentiles Score Minimum 10 20 th percentile 50 48 th percentile 70 68 th percentile 80 90 th percentile 90 (a) Draw a histogram for this data. (b) In what interval is the median value? (c) If possible, identify the exact value of the median. If not possible, explain why not. (d) Will the mean be to the right, to the left, or equal to the median? Explain briefly. (e) The SD of the scores is closest to what multiple of 5? (In other words, is it closest to 5, 10,15, 20, 25, 30, etc.)
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Unformatted text preview: No long calculation necessary, but explain briefly. 2. American Cellular and Computer (AC&C) has 400 employees; their average income is 60,000 dollars and the SD is 25,000 dollars. Another company, Bearizon, has 100 employees; the rms of the incomes at Bearizon is 50,000 and the SD is 30,000 dollars. The two companies merge to form Conglomcast. All 500 employees keep their original salaries. (a) Find the average income for the 100 original Bearizon employees. (b) Find the average income for all 500 Conglomcast employees. (c) Find the SD of all 500 incomes at Conglomcast. 3. A group of students has an average weight of 155 pounds and standard deviation of 25 pounds. The histogram of the weights follows the normal curve closely. (In using the normal table, you can round percents and z values to the nearest value on the table.) (a) About what percentage of the students weigh more than 175 pounds? (b) About what is the 42nd percentile of the weights?...
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