This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
All are true of standardised moality ratio except 
Select and explain. 
A. Expressed as rate per rate, B. can be adjusted for age, C. can be used for events other than death, D. Ratio of observed deaths to expected deaths
A: Expressed as rate per rate
Answer: A: Expressed as rate per rate 
Explanation: ref: Park&;s 23rd edition pg 58 it is expressed as a ratio (usually in percentage) SMR is a ratio of the total number of deaths that occur in a study group to the number of deaths that would have been expected to occur if that study group had experienced the death rates of a standard population (or reference population).