Lists of microbiological and inorganic water quality data are useful to people who want to know the quality of the water in their neighborhood. For a more detailed overview, these are calculated for monthly water quality data by water quality zones (WQZ) and on an overall basis. Descriptive statistics are simple calculations of the characteristics of the data sets.
Descriptive statistics give an overall picture of how water quality varies in the distribution system of Tucson Water. For example, statistics for hardness may show a higher variation of the mean (average) and median in one WQZ as compared to another because water quality may be influenced by wells higher in hardness and other salts.
Besides mean (average) values, other descriptive statistics illustrate how widely dispersed the data is. Standard deviations for certain parameters may be higher than others. Low values of the coefficient of variation also illustrate the low relative differences in data scattered about a mean (average) value. Minimum and maximum parameter values for each WQZ also indicate how widely varying the data can be.
The count of data points used to calculate descriptive statistics in each WQZ is important to show how many sampling points are used. More sampling points are in zones for more densely-inhabited parts of the Tucson Water service area.
Descriptive statistics also show that some water quality parameters vary more than others. For example, Hardness and Total Dissolved Solids (TDS) have a higher variability than pH and Chlorine.
If descriptive statistics are used in conjunction with the Water Quality Zone Map and the individual water quality data points, a better picture of water quality in the Tucson Water service area can be obtained.
All terms shown on this table are explained in Water Quality Terms and Definitions.
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