The students suspected that the very high and very low values were due to the actual drop distance being more or less than 15 centimeters on one of the tubes, not accurately measuring the drop time each trial, or not plotting the data accurately. Removing those highest and lowest values did not change the outcome of the experiment.
Our results for both the gray and black tubes were accurate, but the precision of the gray results was greater than that for the black:
The students theorized that the lower precision of the black tube results was due to the short drop times for that tube, around nine seconds. Slight variations in determining start and stop times had a greater effect on short drop times than on the longer drop times, around 25 seconds for the gray tube.