Quiz1sols - area between.8 and.8 on the standard normal...

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QUIZ 1 Solutions 1) a) Class Interval Count Percent Width Height 10-30 4 8 20 .4 30-50 6 12 20 .6 50-60 5 10 10 1 60-70 8 16 10 1.6 70-80 10 20 10 2 80-90 11 22 10 2.2 90-100 6 12 10 1.2 Y axis: percent/score X axis: score (picture of histogram) b) 70-80 c) 45% to left of 70, then 2% in interval 70-71, and 2% in interval 71-72 makes 50% to the left of 72. Median = 72 d) left tail implies average < med, so average to the left of median. 2) (3 points) mean = (5+9+1+8)/4 = 8 Median = (8+9)/2 = 8.5 SD = sqrt ( (1/4) * ( (5-8)^2 + (9-8)^2 +(10-8)^2+(8-8)^2)) = 1.87 3) (4 points) a) (175 – 155)/25 = .8
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Unformatted text preview: area between -.8 and .8 on the standard normal table is 57.62. Area to right of .8 is (100-57.62)/2 = 21.19 b) the standard units corresponding to 42 % to the left corresponds to 58 % between –SU and SU, or –SU=-.2-.2=(X-155)/25 Solving for X we get X=150 4) 4 points a) Class Interval Percent Width Height 1-2 20 1 20 2-3 30 1 30 3-4 20 1 20 4-6 20 2 10 6-12 10 6 1.667 Y axis: percent/salary X axis: salary (picture of histogram) b) 3000 , 4000...
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