We will use a calculator to find the equation of the line of best fit for the data points. Our first step is to enter the data from the table into our calculator. We do this by pressing the STAT button followed by ENTER. Enter the x-values in the first list and the y-values in the second list.
Next we press STAT again, go to the CALC menu, and press 4, which corresponds to linear regression. Then, we scroll down and press ENTER on the option Calculate.
By doing this we obtain the slope and the y-intercept of the line of best fit, as well as the correlation coefficient.
We can see that the slope of the line is about - 0.23 and its y-intercept is about 25.57. With this information, we can write the equation of the line of best fit in slope-intercept form.
y= - 0.23x+ 25.57
Finally, we also see that the correlation coefficient is about - 0.991. This means that the relationship between the number of days spent training and the race time is a strong negative correlation — the equation closely models the data.
Extra
Setting the Calculator
To obtain the correlation coefficient using our calculator, we first need to make sure that we have turned on the proper settings. To do so, we push 2ND followed by . Then, we scroll down to DiagnosticOn and push ENTER.
