How to calculate the NFF Ratio

When using manufacturer NFF Ratios it is important to be clear how the NFF Ratio has been calculated.

In mathematics any ratio is expressed as:

A:B

which is equivalent to:

A/B

Therefore the NFF Ratio can be expressed as:

No Fault Found : Fault Found

which is equivalent to:

No Fault Found / Fault Found

or:

NFF/FF

Example 1:

Consider the case where we receive 4 units for repair. If 3 of the units are diagnosed as NFF and 1 unit is diagnosed as a FF then we have the following NFF Ratio in percentage terms. NFF Ratio = NFF/FF = 3/1 x 100% = 3 x 100% = 300% Therefore we would have a NFF ratio of 300%.

Example 2:

Consider the case where we receive 4 units for repair. If 1 of the units is diagnosed as NFF and 3 units are diagnosed as a FF then we have the following NFF Ratio in percentage terms. NFF Ratio = NFF/FF = 1/3 x 100% = .3333 x 100% = 33.33% Therefore we would have a NFF ratio of 33.3% (to 1 significant figure)