Q1	Is there a difference between accuracy and precision ?
A1	Yes. Accuracy is the nearness of a result, or the mean (X) of a set of results, to the true value. Accuracy is assessed by means of reference samples and percent recoveries. Precision is the measurement of agreement of a set of replicate results among themselves without assumption of any prior information as to the true result. Precision is assessed by means of duplicate/replicate sample analysis.
Q2	What is a TPH ?
A2	TPH stands for Total Petroleum Hydrocarbons: Low to high boiling point hydrocarbons, including gasoline, kerosene, diesel fuels, thinners, bunker fuels, jet fuels, and oils; determined by EPA Methods 8015M or 418.1.
Q3	What is Relative Response Factor (RRF)?
A3	It is a measure of the relative response of an analyte compared to its internal standard. Relative Response Factors are determined by analysis of standards and are used in the calculation of concentrations of analytes in samples.