Standard time in manufacturing

Standard time is the amount of time that should be allowed for an average worker to process one work unit using the standard method and working at a normal pace. The standard time includes some additional time, called the contingency allowance, to provide for the worker's personal needs, fatigue, and unavoidable delays during the shift.
Calculating the Standard Time.
The standard time (Ts) is calculated from multiplying the observed time (To) by the performance rating (R) and the personal need, fatigue and unavoidable delays (PFD):
Ts = To*R*(1+PFD)