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In statistics, the phi coefficient (or mean square contingency coefficient and denoted by φ or r φ) is a measure of association for two binary variables.. In machine learning, it is known as the Matthews correlation coefficient (MCC) and used as a measure of the quality of binary (two-class) classifications, introduced by biochemist Brian W. Matthews in 1975.
Phi is related to the point-biserial correlation coefficient and Cohen's d and estimates the extent of the relationship between two variables (2 × 2). [32] Cramér's V may be used with variables having more than two levels. Phi can be computed by finding the square root of the chi-squared statistic divided by the sample size.
Phi coefficient. A simple measure, applicable only to the case of 2 × 2 contingency tables, is the phi coefficient (φ) defined by =, where χ 2 is computed as in ...
Archaic form of Phi. Phi (/ f aɪ /; [1] uppercase Φ, lowercase φ or ϕ; Ancient Greek: ϕεῖ pheî; Modern Greek: φι fi) is the twenty-first letter of the Greek alphabet.. In Archaic and Classical Greek (c. 9th to 4th century BC), it represented an aspirated voiceless bilabial plosive ([pʰ]), which was the origin of its usual romanization as ph .
where the Greek letter phi ( or ) denotes the golden ratio. [ a ] The constant φ {\displaystyle \varphi } satisfies the quadratic equation φ 2 = φ + 1 {\displaystyle \textstyle \varphi ^{2}=\varphi +1} and is an irrational number with a value of [ 1 ]
In statistics, Cramér's V (sometimes referred to as Cramér's phi and denoted as φ c) is a measure of association between two nominal variables, giving a value between 0 and +1 (inclusive). It is based on Pearson's chi-squared statistic and was published by Harald Cramér in 1946.
T equals zero if and only if independence holds in the table, i.e., if and only if = + +. T equals one if and only there is perfect dependence in the table, i.e., if and only if for each i there is only one j such that > and vice versa.
the stack alphabet in the formal definition of a pushdown automaton, or the tape-alphabet in the formal definition of a Turing machine; the Feferman–Schütte ordinal Γ 0; represents: the specific weight of substances; the lower incomplete gamma function; the third angle in a triangle, opposite the side c