While we cannot possibly know the “true” value for the gravitational field at the location at which you measured it, we do have two independent measurements for this value:
- The results of your (improved) drop lab.
- The results from the (improved) pendulum lab you just obtained.
We can, at least, compare these two results to each other. For this, we do not use a z-test, but a t-test. The fundamentals of a t-test and the spreadsheet procedure are described below.