Two laboratories measure serum creatinine using different assays. Lab A reports mean 1.2 mg/dL with SD 0.2 mg/dL. Lab B reports mean 0.8 mg/dL with SD 0.15 mg/dL. Which laboratory has greater relative variability?
- A Lab A
- B Lab B ✓
- C Both have equal variability
- D Cannot be determined from the data
Correct answer: B. Lab B
Explanation
Coefficient of variation (CV) measures relative variability and equals SD divided by mean times 100. Lab A CV is 0.2 divided by 1.2 times 100 equals 16.7 percent. Lab B CV is 0.15 divided by 0.8 times 100 equals 18.75 percent. Lab B has greater relative variability despite a smaller absolute SD. Comparing raw SDs without accounting for different means is misleading.
Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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