62. Retail Sales The amount in billions of retail sales by Fuel Dealers for seve
ID: 3057073 • Letter: 6
Question
62. Retail Sales The amount in billions of retail sales by Fuel Dealers for several years from 1992 to 2000 is gi Table 2.16. Let x = 0 stand for 1990, x-1 for 1991, and so forth. ven in (a) Find a quartic regression model, and graph it together with a scatter plot of the data. (b) Find a quadratic regression model, and graph it together with a scatter plot of the data. (c) Use the quartic and quadratic regressions from (a) and (b) to get two estimates of the amount of retail sales for Fuel Dealers in 2005 (d) Writing to Learn Give scenarios to justify each of the estimates in (c).Explanation / Answer
Let me give you TI- 83/84 command to solve this question .
First plug data in calculatior :
Use command as , STAT >>> Edit then press enter . Then in L1 Plug Year data then in L2 column plug Amount Data .
Command : STAT >>> CALC >>>7: QuartReg .
Then for Xlist select year data and for Ylist select Amount data .Then hit enter on calculate .
After that you will get output .
Note : The quartic regression option finds the equation of a cubic equation of the form
y = ax4 + bx3 + cx2 + dx + e that best fits a set of data
Plug values in equation you will get quartic regression equarion.
How to draw the equation :
The equation can be graphed and is transfered to y = without typing the equation as follows.
Press Y = >>> VARS >>>5 : statistics .. Hit enter on Statistics >>> then select EQ.
Press enter on 1: RegEQ to enter the regression equation and press . The equation is now entered in .
Press GRAPH .The data points can also be viewed. Access STAT PLOTS by pressing 2ND >>> Y= >>> 5 : Statistics to turn the plots on.
Press Enter .You will see graph on Calculator
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2) How to find Quadratic Regression model :
All part is same . Just use command as , Press STAT, >>>arrow right to CALC, >>>> 5: QuadReg. Hit ENTER.
Then enter values . then hint enter on calculate .You will get output .
An equation of the form: Y=ax2+bx+c where a0 .
Plug values from output roy will get eauation .
Use same method for graph just plug above equation in Y = ..
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