Complete the table and plot a graph of T2 against l for a simple pendulum experiment.

This step requires plotting on graph paper, which cannot be done here. However, I can provide the data points for plotting.
The points to plot are $(l, T^2)$:
$(1.00, 4.038)$
$(0.90, 3.620)$
$(0.80, 3.249)$
$(0.70, 2.881)$
$(0.60, 2.403)$
$(0.50, 2.074)$

The formula for the period of a simple pendulum is $T = 2\pi\sqrt{\frac{l}{g}}$.
Squaring both sides gives $T^2 = 4\pi^2 \frac{l}{g}$.
This equation is in the form $y = mx$, where $y = T^2$, $x = l$, and the slope $m = \frac{4\pi^2}{g}$.

To find the slope, we can use two points from the calculated data. Let's use the first and last points for better accuracy.
Point 1: $(l_1, T_1^2) = (1.00 \text{ m}, 4.038 \text{ s}^2)$
Point 2: $(l_2, T_2^2) = (0.50 \text{ m}, 2.074 \text{ s}^2)$

From the relationship $m = \frac{4\pi^2}{g}$, we can find $g$.