Wednesday, November 3, 2010

Ch.2 Project

I have choose the MINI Cooper for my chapter 2 project. I found out the mileage for the car in For the speeds 55, 60, 65, 70, 75, 80 in miles per hour, the mileage (miles per gallon) are 37, 35.9, 34, 30.7, 28.5, 26.6 . Next I plot the points using speed as the independent variables and the mileage as the dependent variables. Since the points are going down, the graph have a negative slope that mean it also have a negative correlation. Next, I sketch the line best fit on the graph. The 2 points I choose to find the slope with is (60,35.9) and (80,26.6); doing the calculation Y1 - Y2 over X1 - X2 I got the slope -9.3/20. To use the informations I already have to write an equation I set up the point-slope form first which is y-26.6=-9.3/20(x-80) turning it to slope-intercept form the equation is y=-9.3/20x+63.8 . Using the calculator to find the value of correlation coefficient r, r=-.9917995234. The value of r tell me that the as speed get higher is the mileage will go lower, because r is close -1 coefficient. By using the graphing calculator to find the equation for the line best fit I get y=-.4428571429x+62.00952381 . To predict the mileage for a speed of 55 miles per hour, I type in : y(55) in my calculator, the mileage is 38 (miles per gallon). To predict the speed if the milage is 28 miles per gallon we can't use the same method because 28 is y in the equation, so I plug 28 in as y, 28=-.4428571429x+62.00952381. After isolating x (speed) the answer is 77 miles per hour.

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