Among miners employed for 20 years, 120 deaths from respiratory disease were observed. Using national age-specific rates applied to the miner population, 80 such deaths were expected. The standardized mortality ratio (SMR) is:

• A 67 percent
• B 120 percent
• C 150 percent ✓
• D 180 percent

Explanation

SMR equals observed deaths divided by expected deaths multiplied by 100, here 120 divided by 80 times 100, giving 150 percent. This means miners experienced 50 percent excess respiratory mortality compared with the standard population after adjusting for age structure. An SMR of 100 would indicate mortality identical to the reference population, and 67 percent corresponds to the reciprocal calculation, expected over observed, which is incorrect.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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