In my university we had a more precise setup for that. It was some sort of weight on a rail at a known incline, and a digital timer with two sensors known distance apart that start and stop it.

Yet in my class we still had results as low as 7 and as high as 12. We all got passing grades. But the protocol for these lab assignments was always such that you had to have your "measurements sheet" signed by the professor, and you turned it in with your report later.