It is impossible to make an exact measurement. Therefore, all experimental results are wrong. Just how wrong they are depends on the kinds of errors that were made in the experiment. Scientists know that their results always contain errors. However, one of their goals is to minimize errors, and to be aware of what the errors may be.
Significant digits is one way of keeping track of how much error there is in a measurement.
Since they know that all results contain errors, scientists almost never give definite answers. As a science student you too must be careful to learn how good your results are, and to report them in a way that indicates your confidence in your answers . There are two kinds of experimental errors. Random Errors These errors are unpredictable. They are chance variations in the measurements over which you as experimenter have little or no control.