Percent Relative Average Deviation

The results only give an indication about precision; they give no indication of accuracy. Accuracy is a measure of how close the results are to a known literature value; however, because a known molarity for the hydrochloric acid is not known, a measure of accuracy cannot be made.

In contrast, a measure of precision can be made using the results. Precision refers to how close a set of results are to each other. In this lab, the percent relative average deviation can be used as an indicator of preciseness. Percent relative average deviation is a measure of how tightly clustered a set of data points is around a mean. A low percent relative average deviation indicates that the data points are tightly clustered around the mean; moreover, if the
The difference in the calculated molarities using the first and second endpoint data may be the result of experimental error, which is discussed in the next section.

Where might experimental error have occurred? (Do not use the phrase human error, describe errors as it is believed they occurred.)

The major contributor of experimental error in this lab may be titrating beyond the endpoint. Due to inexperience with the indicators and their endpoints, it was apparent that the titrations may have gone beyond the endpoint. If this did occur, then the volumes of hydrochloric acid used to neutralize the sodium carbonate would be too great. This, in return, would erroneously decrease the molarity of the hydrochloric acid since the volume would increase while the moles of hydrochloric acid used would stay