Skip to section navigation Skip to main content

Exploring Other Function Models

Test and Confirm

Khalid graphs the quadratic regression equation with the scatter plot data, as seen below.

This graph is a scatter plot displaying the price (in dollars) per 1000 cubic feet of natural gasoline over a six month period.  The graph is titled ‘Natural Gasoline Prices.’  The horizontal axis is labeled ‘Month’ and extends from negative 2 to 10.  The vertical axis is labeled ‘Price (in dollars) per 1000 cubic feet’ and extends from negative 2 to 24.  The graph displays the following ordered pairs:  (0, 16.09), (1, 14.40), (2, 12.26), (3, 10.29), (4, 9.13), (5, 9.41), and (6, 11.78).  The curve defined by function f of x = 0.405x2 minus 3.36x + 16.724 is drawn through the scatter plot.

kahlid holding a calculator and speakingKhalid: From the graph, it looks like a quadratic model is a good fit.  But, I still need to check the residuals and examine the residual plot.

Khalid needs to verify that a quadratic model is the most appropriate model for this data set.  To do this he will need to analyze the residual plot to verify that the residuals are small and the plot does not reveal a pattern.  If the residual plot is not ideal, he will need to examine other potential models to see if there may be a better fit. 

Using your graphing calculator, graph the residual plot.  When ready, move to the next page.



< Previous Next >