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Precision and recall. In statistical analysis of binary classification and information retrieval systems, the F-score or F-measure is a measure of predictive performance. It is calculated from the precision and recall of the test, where the precision is the number of true positive results divided by the number of all samples predicted to be positive, including those not identified correctly ...
Piotroski F-score is a number between 0 and 9 which is used to assess strength of company's financial position. The score is used by financial investors in order to find the best value stocks (nine being the best). The score is named after Stanford accounting professor Joseph Piotroski. [1]
In a classification task, the precision for a class is the number of true positives (i.e. the number of items correctly labelled as belonging to the positive class) divided by the total number of elements labelled as belonging to the positive class (i.e. the sum of true positives and false positives, which are items incorrectly labelled as belonging to the class).
The F table serves as a reference guide containing critical F values for the distribution of the F-statistic under the assumption of a true null hypothesis. It is designed to help determine the threshold beyond which the F statistic is expected to exceed a controlled percentage of the time (e.g., 5%) when the null hypothesis is accurate.
An F-score is a combination of the precision and the recall, providing a single score. There is a one-parameter family of statistics, with parameter β, which determines the relative weights of precision and recall. The traditional or balanced F-score is the harmonic mean of precision and recall:
A common way to do this is to state the binomial proportion confidence interval, often calculated using a Wilson score interval. Confidence intervals for sensitivity and specificity can be calculated, giving the range of values within which the correct value lies at a given confidence level (e.g., 95%).
The Piotroski F-score is a 9-point valuation metric derived on this research. Through back-testing, Piotroski found that buying the top stocks in the market according to his methodology and shorting those that got the worst scores would have resulted in 23% annualized gains from 1976 through 1996, more than double the S&P 500 broad market index ...
A score of above 80 on the F-scale test indicates that the subject may be suffering from severe psychopathology. Patients who suffer from repeated episodes of disorders usually get a higher F-scale score than those who have acute disorders. Research has not found any correlation between F-scale scores and educational level. [citation needed]