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As you saw before, part of the between laboratories variation was caused by variation in the nitrogen-to-protein conversion factors that were used. Below you see the table in which the results are recalculated using conversion factors recommended by the FAO/WHO (figures in red are the recalculated).

Not right. Note that the recalculated CV between is lower than the original CV between. This means that if the same conversion factors were used by all laboratories the CV between will be lower.

Not right. For Rye, wheat and biscuits the difference between the recalculated CV between and the original CV between is considerable.

Not completely right. If the same conversion factors were used by all laboratories the CV between will be lower. However, there will remain some variability between the laboratories. This means that the use of different conversion factors only partly explains the differences between laboratories.

Not completely right. You can assume that WITHIN laboratories the same conversion factors are used. So the use of the same conversion factors by all laboratories will not influence the CV within.

Right.

Summarized, from this interlaboratory trial it can be concluded that

• The discrepancies in protein values between laboratories are rather small, but for some foods still higher than expected.

• Variability between laboratories will decrease if all laboratories use the conversion factor recommended by the FAO/WHO. This is especially the case for protein values of cereals.

• The difference between duplicate values is quite high in some laboratories.

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