This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostats, Subject name: Social & Preventive Medicine
Intraocular pressure (IOP) was measured in 400 people. Mean was found to be 25 mm Hg and Standard detion was recorded 10 mm Hg. 95% Confidence Interval would be? 
Select and explain. 
A. 22-28, B. 23-27, C. 24-26, D. 21-29
C: 24-26
Answer: C: 24-26 
Explanation: In the given question, Mean (u) = 25 mm Hg standard detion = 10 mm Hg, Z95 = 1.96 (as we are asked 95% CI) Sample size, n =400 Confidence intervals (CI 95) = Mean +- Z95 (SE) CI-95 = 25 +- 1.96 (10/ [?]400) = 24-26 mm Hg