Skill Score Overview - MATS Documentation

Updated: January 12, 2026

The following are all of the skill scores that are used for verification inside MATS applications, an explanation of what the cells of the contingency table represent, and the algorithms being used for each:

Contingency Table¶

Forecast	Observed
Forecast	Yes	No
Yes	a (Hit)	b (False Alarm)
No	c (Miss)	d (Correct Null)

Skill Scores Needed¶

Critical Success Index (CSI)¶

{\frac{a}{a+b+c}}

(1)

Bias (fcst/observed)¶

{\frac{a+b}{a+c}}

(2)

PODy (POD of refl > thresh)¶

{\frac{a}{a+c}}

(3)

PODn (POD of refl < thresh)¶

{\frac{d}{d+b}}

(4)

False Alarm Ratio (FAR)¶

{\frac{b}{b+a}}

(5)

True Skill Score (TSS)¶

{\frac{a}{a+b}} + {\frac{d}{d+c}} - 1

(6)

Heidke Skill Score (HSS)¶

2 *{\frac{d*a - c*b}{(d+b)*(b+a) + (d+c)*(c+a)}}

(7)

Fcst Ratio (fcst/total)¶

{\frac{a+b}{a+b+c+d}}

(8)

Obs Ratio (obs/total)¶

{\frac{a+c}{a+b+c+d}}

(9)