quiz3soln

# quiz3soln - be bigger since regression line is not as steep...

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STAT 21 SP 09 QUIZ 3 Solution 1. (3pts) (1) (1pt) standard unit of x = 0.33 (2) (1pt) multiply by r = 0.27 (3) (1pt) convert from standard unit to real data = 101. 2. (5pts) (1) (2pts) standard of unit of x = -0.2 multiply by r = -0.14 convert out of standard unit = 26.6 (2) (1pt) calculate the r.m.s. error = 7.14 (3) (1pt) calculate the z -value = 0.34 (4) (1pt) look up the area to the right = 36.32 or 36 or 37. 3. (4pts) (1) (2pts) choose (ii) is less than (2) (2pts) explanation: Regression e ect says predicted value should be closer to average (50th percentile) and thus bigger than 31st percentile, so this is less than pre- dicted. This point is on the SD line, and the value on the regression line has to

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Unformatted text preview: be bigger since regression line is not as steep. 4. (8pts) (1) (2pts) Sample 1 2 3 4 5 ave sd x 14 16 6 11 12 11.8 3.37 y 108 110 145 121 118 120.4 13.22 xy 1512 1760 870 1331 1416 1377.8 r =-0.96 (2) (1pt) m =-3.78 1 2 (3) (1pt) b = 164.98 (4) (1pt) predicted y =-3.8 x + 165, must include the word predicted. (5) (1pt) No. (6) (1pt) Association is not causation. (7) (1pt) Interpretation of the slope: people who eat more meals cooked by vegetable oil tend to be lighter. If one person eats one more such meal per week than another person, the ﬁrst person will be, on average, about 3.8 pounds lighter....
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## This note was uploaded on 07/08/2010 for the course STATS 21 taught by Professor Ibser during the Spring '09 term at Berkeley.

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quiz3soln - be bigger since regression line is not as steep...

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