what are some weaknesses of this experiment?
an experiment on how much water i waste while brushing my teeth. (i timed my self for 21 days). this compared to the amount an average american wastes - an extimate i found online.
what are some weaknesses. as many as possible please.
First, a strength - timing yourself for 21 days, rather than just once, was a good idea.
As far as weaknesses, timing only yourself is a major weakness. We have no way of knowing if you are an "average" brusher. In a well-designed experiment, you would need to have a large group of people all agree to participate as brushers.
How did you translate the time the faucet ran into a volume of water? If you didn't do this, you probably should - run the faucet into a container for a known amount of time (perhaps 10 seconds), measure the water in the container, and divide by the time to get a volume per second. (This would have to be done for every faucet used by every participant.)
Also, did you turn the faucet on all the way every time? If not, then your measurements are questionable - if one day you turned the faucet on to 80% of its maximum flow, but then the next day you turned it on to 75%, then timing the flow doesn't mean much.
Finally, I would suggest that you take a very careful look at the source of the estimate you found online for credibility, as well. As we have just shown here, it's a difficult number to get.