In a study, when the sample size is increased from 100 to 400, the standard error of the mean (SEM) will:

• A Halve ✓
• B Double
• C Remain the same
• D Increase fourfold

Explanation

SEM = SD / √n. When n increases 4-fold (100 to 400), √n increases 2-fold (10 to 20), so SEM = SD/20, which is half of SD/10. Therefore SEM halves when sample size quadruples. This demonstrates why larger samples give more precise estimates: the standard error (precision of the mean estimate) decreases as sample size increases.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.