Data of unknown quality are useless! All laboratory measurements contain experimental error. It is necessary to determine the magnitude of the accuracy and reliability in your measurements. Then you can make a judgment about their usefulness. Replicates - two or more determinations on the same sample Example 3-1: One student measures Fe (III) concentrations six times. The results are listed below: , , 19. 6, , , ppm (parts per million) 6 replicates = 6 measurements The "middle" or "central" value for a group of results: Mean: average or arithmetic mean .
