Getting averages from your results
You will probably do your experiments more than one time. When you do that, even though you think nothing has changed, you may still find that your measurements are not identical. This is for x reasons:

  1. It’s hard to measure something precisely with your measuring tools. Results may fall between marks on a ruler or measuring cup. If you‘re using a timer, you may click it slightly differently each time. Things like that are expected, and they won’t hurt the experiment. Just try your best to make measurements the same way each time.
  2. There will also be slight variations in how the experiment is run, things you may not even be aware of. You might give something a little push when you’re releasing it. There might be some little wind in the room when you’re “sailing” an airplane. Rolling objects encounter friction that may slow them down; an uneven surface may produce more friction for some trials than for others. Things like that.

Even if you have controlled the variables as closely as you can, your results will be close to each other, but different enough to make it hard to know which is the “best” measurement. That’s why we have averages.

Averages are easy to calculate.

  1. Add up all the results to get a single number.
  2. Count how many numbers you added up (that’s the number of trials you ran)
  3. Divide the total results by the number of trials.
  4. The result is the average value, the result that falls closest to the middle of all the trials. That will be the best number to represent that set of trials.
When you compare results of different sets of trials, compare the averages. That will be the best way to interpret your results.

Example of an average:
Distance a ball rolls from the top of a ramp.

Trial 1: 5.8 meters (or feet or inches)
Trial 2: 6.1 meters(or feet or inches)
Trial 3: 6.0 meters(or feet or inches)
Trial 4: 6.3 meters(or feet or inches)
Trial 5: 5.9 meters(or feet or inches)

Add up the results: 30.1 meters(or feet or inches)
Divide by the number of trials: 5
Average time: 6.02 meters(or feet or inches)

The average may be slightly different from any of the actual measurements, but it is going to be the result that means the most.

See, easy!