Measurement is within the interquartile range (IQR), defined as the 25th to 75th percentile or middle half (50%) of the measurements. Examples: sulfate, ammonium, sodium, and potassium.
Measurement is within the range defined by the median + IQR/1.349. The ratio, IQR/1.349, is the non-parametric estimate of the standard deviation, sometimes called the pseudo-standard deviation. Examples: nitrate, chloride, and calcium.
Measurement is outside the range defined by the median + IQR/1.349. Examples: pH, conductivity, and magnesium.
Measurement is below the detection limit of the laboratory’s analytical method. Example: fluoride.
|pH||+ 0.07 units|