20-hw2-students - Stat 20 solutions to homework 2 Michael...

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Stat 20: solutions to homework 2 Michael Lugo September 14, 2010 Ch. 4, Review: 4, 7, 9, 10. Ch. 5, Review: 2, 3, 8, 11. Chapter 4, # 4 The average income is definitely higher than the median income, because some people with very large incomes will skew the results upwards, while people with very small incomes don’t have this same effect. For years of schooling completed, the median is higher than the average. The median is probably around 12; it’s easy to be far below the median but hard to be far above the median. Chapter 4, # 7 (a) Multiplying everything by 2.2, the men have average weight 145.2 lb, the women have average weight 121 lb, and both have SD 19.8 lb. (b) 68%. (c) Bigger than 9 kilograms. The SD measures, roughly, how much the distribution is spread out; the combined distribution is spread out over a wider region than either the men or women alone. Chapter 4, # 9 (a) It affects the average. The total income of all families rises by 986 , 000 - 98 , 600 = 887 , 400, so the average of all 1 , 000 of them gets raised by 887 , 400 / 1 , 000, or 887 . 40 dollars.
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