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What is Following can be used as a yardstick for the  assessment of standards of therapy - and explain in detail?
Survival rate 

It is the proportion of survivors in a group (e.g. of patients) studied and followed over a period of time.
It is a method of describing prognosis in certain disease conditions.
Survival experience can used as a yardstick for the assessment of standard of therapy.
Survival rates have received special attention in cancer studies.

5 years of survival rate = Total no. of patients alive after 5 years / Total no. of patients diagnosed or treated x 100

Survival period is usually reckoned from the date of diagnosis or start of the treatment.