Question

In: Statistics and Probability

Summarizing Bivariate Data (1) The data in table below represent airline fuel cost per gallon (in...

Summarizing Bivariate Data

(1) The data in table below represent airline fuel cost per gallon (in dollars) for the US

domestic and international carriers with scheduled service by month from July 2014 to

December 2014.

Month Domestic (x) International (y)

July 3 2.84

August 2.98    2.84

September 2.89 2.81

October 2.69 2.67

November 2.58 2.55

December 2.3 2.3

(a) Find the correlation coefficient value r.

(b) If we wish to predict international cost using the domestic cost, identify response and

predictor.

(c) Find slope and intercept of the regression equation of y on x.

(d) Write out the regression equation of y on x.

Solutions

Expert Solution

Excel sheet: Values

Sxx Syy Sxy
Domestic (X) International (Y) X2 Y2 XY (X-Xbar)2 (Y-Ybar)2 (X-Xbar)(Y-Ybar)
3 2.84 9 8.0656 8.52 0.0676 0.029469 0.044633
2.98 2.84 8.8804 8.0656 8.4632 0.0576 0.029469 0.0412
2.89 2.81 8.3521 7.8961 8.1209 0.0225 0.020069 0.02125
2.69 2.67 7.2361 7.1289 7.1823 0.0025 2.78E-06 -8.3E-05
2.58 2.55 6.6564 6.5025 6.579 0.0256 0.014003 0.018933
2.3 2.3 5.29 5.29 5.29 0.1936 0.135669 0.162067
Total 16.44 16.01 45.415 42.9487 44.1554 0.3694 0.228683 0.288
Mean 2.74 2.668333
Variance 0.061567 0.038114 Slope 0.779643
SD 0.248126 0.195228 intercept 0.532112
Covariance 0.048
Correlation 0.990893

Excel sheet: Formula

Sxx Syy Sxy
Domestic (X) International (Y) X2 Y2 XY (X-Xbar)2 (Y-Ybar)2 (X-Xbar)(Y-Ybar)
3 2.84 =B3^2 =C3^2 =B3*C3 =(B3-$B$10)^2 =(C3-$C$10)^2 =(B3-$B$10)*(C3-$C$10)
2.98 2.84 =B4^2 =C4^2 =B4*C4 =(B4-$B$10)^2 =(C4-$C$10)^2 =(B4-$B$10)*(C4-$C$10)
2.89 2.81 =B5^2 =C5^2 =B5*C5 =(B5-$B$10)^2 =(C5-$C$10)^2 =(B5-$B$10)*(C5-$C$10)
2.69 2.67 =B6^2 =C6^2 =B6*C6 =(B6-$B$10)^2 =(C6-$C$10)^2 =(B6-$B$10)*(C6-$C$10)
2.58 2.55 =B7^2 =C7^2 =B7*C7 =(B7-$B$10)^2 =(C7-$C$10)^2 =(B7-$B$10)*(C7-$C$10)
2.3 2.3 =B8^2 =C8^2 =B8*C8 =(B8-$B$10)^2 =(C8-$C$10)^2 =(B8-$B$10)*(C8-$C$10)
Total =SUM(B3:B8) =SUM(C3:C8) =SUM(D3:D8) =SUM(E3:E8) =SUM(F3:F8) =SUM(G3:G8) =SUM(H3:H8) =SUM(I3:I8)
Mean =B9/6 =C9/6
Variance =(D9/6)-(B10^2) =(E9/6)-(C10^2) Slope =I9/G9
SD =SQRT(B11) =SQRT(C11) intercept =C10-F11*B10
Covariance =(F9/6)-(B10*C10)
Correlation =B13/(B12*C12)

a) r=0.99

b) Response: International carrier

Predictor: Domestic cost

c) Slope = 0.7796 and intercept = 0.5321

d) y=0.5321+0.7796 x

international carrier = 0.5321+0.7796 Domestic cost


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