Precision - how carefully and exactly you make your measurement, and the regularity of obtaining the same result
If scientific results are both accurate and precise, they are considered to be valid and true, and is therefore reliable.
When we did our experiments with the m&ms. We realized that we were not being very precise, our results were not reliable. We changed the way we conducted the experiments to make our measurements more precise, which meant our tests were more reliable.
Different situations call for the amount of precision required. If you asked me how long it takes me to drive to Melbourne, I would say 1/2 an hour (even if it only takes me 26 minutes) we round time up and down, because we know that the person asking that question doesn't need such a precise answer. If you asked an runner what their quickest time is to to run 10km, they would give you a more precise time, they might say 43 minutes and 24.7 seconds. Both answers are accurate, but the precision depends upon the amount of information required.
If I asked you how long your desk is, you might say 1.5 m, 152cm, or 1523mm. All are accurate, but one is more precise. Which one would be the answer you would give? Our precision depends on who requires the information, or why they require the information. The smaller the measurement unit, the greater the precision.
If I'm an archer and hit the target in the bullseye I have been accurate. If I continue to hit the target in the bullseye, I will be showing precision. If I don't continue to hit the bullseye, I have been accurate with one shot, but not precise. If I keep hitting the tree next to the target, I am being precise, but not accurate.
Confusing huh?
To summarize:
The precision of a measurement is the size of the unit you use to make a measurement. The smaller the unit, the more precise the measurement.
The accuracy of a measurement is the difference between your measurement and the accepted correct answer. The bigger the difference, the less accurate your measurement
www.worsleyschool.net/science/files/precision/andaccuracy.html
Here's a link to a Brainpop game about Precision:
Battleship Number Line
