Ch.2 Project

I have choose the MINI Cooper for my chapter 2 project. I found out the mileage for the car in http://www.mpgforspeed.com/. 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.