Nonlinear Heart Rate Variability features for real-life stress detection. Case study: students under stress due to university examination

Table 2 Binary Classification Performance Measures

Measure	Abbreviation	Formulae
Total classification accuracy	ACC	$\frac{T P + T N}{T P + T N + F P + F N}$
Sensitivity	SEN	$\frac{T P}{T P + F N}$
Specificity	SPE	$\frac{T N}{F P + T N}$
Positive Predictive Value	PPV	$\frac{T P}{T P + F P}$
Negative Predictive Value	NPV	$\frac{T N}{T N + F N}$

TP: the number of records performed during university examination correctly detected
TN: the number of records performed on holidays correctly detected
FP: the number of records performed on holidays incorrectly labelled as during university examination
FN: the number of records performed during university examination incorrectly labelled as on holidays.

ISSN: 1475-925X