Verified answer

Here is a graphing idea for how to display just how they compare:

http://img51.imageshack.us/img51/2951/freefallpara...

Remember: air drag will distort your results, acting as a force that you aren't able to yet consider. That is why it is best you use simple shaped objects of high density to conduct these experiments.

This is precisely why there is more uncertainty and less achieved acceleration for your lower mass object....air drag is more significant. Look at your higher mass object, and you see that you have less uncertainty, and your acceleration is much closer to the literature value of Earth's free fall acceleration (9.8 m/s^2 in San Francicso).

Alternatively, you can conduct experiments in a vacuum chamber (less practical).

I'm not sure you have enough data. Maybe you need more than 3 trials

You would calculate a mean and standard deviation (or standard error, I forget) for each different weight. So you get something like

57 g : 1.72 +/- 0.02

10g : 1.80 +/1 0.05

then if the results for different mass are the same within experimental error, you can say that different masses accelerate at the same rate to an accuracy of 1%, or whataver