An analysis is usually conducted by replicated sampling or repeated measurements on the same sample. This leads to scattered results rather than a single value. The difference between the obtained results and the true or expected value, or the central value, is known as the error in that measurement. The central value in a set of scattered results is the estimated mean or median. The Mean is the ratio between the sum and the total number of replicate measurement values. Alternatively, the median is the middle value amongst the records, arranged in an increasing or decreasing order. The range is the numerical difference between the largest and smallest values in the replicate measurements. Precision indicates the closeness between different replicate measurements. Accuracy reflects the closeness of a measurement to the true or central value. Statistical analysis can categorize and characterize the results of an analysis to make an objective decision about data quality.