After doing the Pit and Pendulum, we tried to estimate how long a 30 foot pendulum would take based off of the other, shorter pendulum swings. Based off of the other pendulums, I guessed the 30 foot one would take around 8.4 seconds for one swing. However, it was a lot closer to 7.08.
This could be based on a number of things like weight, or how we did the experiment outside. Most likely, it was just miscalculations on our part, either by my estimate or by how we timed the 30 foot pendulum's swing time.