Use your calculator to draw a scatter plot of the data.
Example model: y=0.0998x^2-0.4978x-5.0072 Example estimate: 32 tons
Practice makes perfect
Let's use the calculator to draw a scatter plot of the data.
Push the STAT button, choose Edit, and enter your values.
Once the values have been entered we can plot them by pushing 2nd, Y=, and then choosing one of the plots in the list. Make sure you turn the plot ON before you choose the scatter plot type. Then, match the lists for the x- and y-values accordingly.
By pushing GRAPH the calculator will plot the data. Note that we will need to change the viewing window so that we can see all of the points.
We can see an increasing trend with a bit of curve, so let's use a quadratic regression.
We can access this option by pressing the STAT button and choosing QuadReg from the CALC menu.
After matching the lists for the x- and y-values and setting the place to store the equation, move to the last line and press ENTER.
The result screen gives the coefficients of the quadratic model.
y= ax^2+ bx+c
⇓
y= 0.0998x^2+( -0.4978)x+(-5.0072)
Since the regression equation is now stored in the memory of the calculator, when we press GRAPH again we can see the regression line with the scatter plot.
We can use the calculator to estimate the weight supported by ice that is 22 inches thick.
Push 2nd and TRACE, choose value from the menu and set x=22.
We can also check this result by substituting x=22 in the regression equation.
We can see that the calculated value and the value the calculator gives are approximately the same.
The reason for the difference is that we used rounded values for the coefficients.
The estimated weight supported by ice that is 22 inches thick is 32 tons
