y = 0.0015 x^3.1239

For a power function

• y = a x^p

there are only two parameters.

So if we know two points on the graph we can find a and p, and we'll know the function.  However, it's not easy at this point of the course to solve for a and p.

Sometimes we have a pretty good idea what p should be. 

If we think we already know p, then we need only one point to evaluate a.

But we check several points and see if our a values are consistent. 

That is, if we use several points, and evaluate a separately for each point, then if our a values are all about the same, we know our p value is pretty good.