Question 1131770
There are 4 data points (2,7); (1,3); (3,8); (4,10)
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The mean of the x values is (2+1+3+4)/4 = 2.5
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The mean of the y values is (7+3+8+10)/4 = 7
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The standard deviation of the x values is square root(((2-2.5)^2 +(1-2.5)^2 +(3-2.5)^2 +(4-2.5)^2)/(4-1)) = 1.29
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The standard deviation of the y values is 2.94
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The correlation factor(r) is ((1/(4-1)) ((2-2.5)*(7-7) +(1-2.5)*(3-7) +(3-2.5)*(8-7) +(4-2.5)*(10-7))/(1.29*2.94)) = 0.9668
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slope(b) of the regression line = 0.9668 * 2.94 / 1.29 = 2.2034
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a = 7 -2.2034 * 2.5 = 1.4915
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a) Y = 2.2034X +1.4915
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b) Y = bX +a, b = 2.2034 and a = 1.4915
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Note a is the y intercept of the regression line and b is its slope 
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c) y = 2.2034 * 3 + 1.4915 = 8.1017
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When $3 million is spent on advertising, the estimated sales is $8.1017 million
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