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Quiz1Sols

# Quiz1Sols - If mean is less than 70(it probably is then...

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Quiz 1 Solutions Statistics 21 Spring 2010 Ibser Each part of every problem is worth 2 pts except 1a worth 3 and 1b worth 1. 1. (a) Interval Percent Height 10-50 20 0.5 50-70 28 1.4 70-80 20 2 80-90 22 2.2 90-100 10 1 Draw histogram with these axes: x axis: Scores (or Points) y axis: percent per score (or percent per point) (b) 70-80 (c) Since height in that bar is 2 percent per score, and 48% below 70, 71 is the median. (d) mean to the left of the median, long left tail (or skewed left) (e) 20. If mean is around 70, going 20 pts each way would capture (about) 70%, which is pretty close to 68%.
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Unformatted text preview: If mean is less than 70 (it probably is) then area would be slightly smaller, so even closer to 68%. 15 each way would only get about 52%, 25 each way would get about 77.5%, so these don’t work as well. 68% is from the normal curve, so not exact, but should be fairly close for this histogram, which isn’t terribly skewed. 2. (a) 40,000 (b) 56,000 (c) ssq for AC&C: 1,690,000,000,000 and ssq at Bear: 250,000,000,000 ssq at Cong: 1,940,000,000,000 answer: 27,276 3. (a) (175-155)/25 = 0.8; about 21.2 % (b) z=-0.2; 150 pounds...
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