What are errors for Serial Dilutions for viable counts?
With each sequential serial dilution step, transfer inaccuracies lead to less accurate and less precise dispensing. The result is that the highest dilutions will have the most inaccurate results. For example, even though the pipette is set to dispense 5ml each time, the actual volume can vary within 1-100ul depending on the accuracy of the pipette and pipetter. Also, after every innoculation, the dilution must be thoroughly mixed. Theoretically, longer mixing times are required for more dilute samples, however, this is usually not compensated for and unequal concentrations are usually used to innoculate the next dilution. Finally, when doing viable counts, the higher dilution is, the more error is found in “estimating” the count of the original volume. For example, if we find 5 colonies growing on the 10^3 plate, then we estimate there were approximately 5000 colonies in the original suspension, but we are really only estimating to the closest thousand. Likewise, if we use a higher dil
