With the method we used to calculate the reachable height, there are many ways in which errors or inaccuracies could have been introduced in to our measurements. We had people in our group that consisted of varying heights, weights, etc that put different limits on our individual heights. However, collectively, the process of jumping up and sticking pieces of tape against the wall isn't nearly as accuracte as it possible could be. Instead, laser sights, slow motion cameras and other things, such as the equipment commonly seen in Mythbusters, could provide more accurate data. With this things you can maximize your results accuracy. If people had the equipment doing the work such as "putting a label" where there maximum height is, then they'd be able to focus more on just jumping, instead of multi tasking. While in mid-air theres a slight delay before you place a peice of tape on the wall, which means that most likely the tape is LOWER than what your capable of. Also, there really aren't any guidelines that instruct you how to jump, if you should be moving, things like that. With this its clear to see that if there were better techniques available, then the percent error would be lower as well.