Answer
The least precise is the graphical method because reading coordinates of points on a graph is working with estimated values.
Work Step by Step
We determined the average rate of change of $f$ over an interval $[a, b]$
1. numerically, $\displaystyle \frac{f(b)-f(a)}{b-a}$, using a table of values.
2. graphically, by measuring the slope through two points on the graph.
3. algebraically, by using an algebraic formula for the function.
The least precise is the graphical method because reading coordinates of points on a graph is working with estimated values.
