In the laboratory neither the measuring instrument nor the measuring procedure is ever perfect; consequently, every experiment is subject to experimental error.  The Experimental Precision and Error simulation explores how the precision of a measuring device affects the accuracy of the measurement. The precision of a measuring device refers to the smallest increment or unit of measurement that the device can reliably measure. For a ruler, this would be the smallest division marked on it. For example, if a ruler has markings every millimeter, its precision is 1 millimeter.

Both precision and accuracy are important when making measurements. Precision determines how finely a measurement can be made. The more precise a measuring device is, the smaller the unit it can measure, allowing for more detailed and accurate measurements. Precision should not be confused with accuracy, which refers to how close a measured value is to the true value. Since experimental errors are unavoidable, what can be done to increase our confidence in our results?