Piotroski F-score is a number between 0 and 9 which is used to assess strength of company's financial position.
[2] Some adjustments that were done in calculation of the required financial ratios are discussed in the original paper.
Average value of Piotroski F-score can be different in different branches of economy (e.g. manufacturing, finance, etc.).
The Piotroski F-score is a method invented or thought up a few decades ago.
Since realities are no longer what they were when it was conceived, it can happen that this strategy, although effective, suffers from some shortcomings.