The next task is to make a linear regression line
in order to find the exact speed
at which to throw the balloon. To do this, press
, select the CALC menu, and select item 4: LinReg(ax+b) (Fig. II.1),
then press enter twice (Fig. II.2).
If your calculator does not display "r" or "r2
," you can press 2nd then 0 to go to the catalog, and select the item "Diagnostic On" and press enter twice. Now repeat the first step.
"r" and "r2
" are used to determine how well the line
fits the data. "r2
" is simply "r" multiplied by itself and is always between 0 and 1. "r" can be any value between -1 and 1. An "r" value of -1 or 1 means you have a perfect fit. As "r" values get closer to 0, the less correlation there is in your data.
, and clear all the equations. Go to Y1
, select item 5: Statistics... Go to the EQ menu, and select item 1: RegEQ and press enter (Fig. II.3).
should now appear in the Y1
, and you should see the regression line
appear over top of the points (Fig. II.5).
To find when this line
equals 3, you will have to press
again, and type 3 into the Y2
. Then use the technique learned in "Police and Neon" to find the intersection
of the two lines. The x
value of this intersection
is the speed
at which the ball would need to be thrown (Fig. II.6).