Why should I have ChemStat convert all values to ppb?
It is possible to import data without converting to parts-per-billion, but the conversion is recommended. All statistical comparisons must be with consistent units. ppb was chosen because it is commonly used and it is rare to have detected values below 1 ppb. It is important that your statistical data all be 0 or greater than 1. Otherwise, log transformations produce negative numbers. ChemStat will still work with values less than 1, but you must be careful taking the log of such values.
