Social & Preventive Medicine Biostatistics 04e781bf Area under normal curve within +- 1SD (standard detion)- A 0.68 B 0.17 C 0.12 D 0.34 High-Yield Explanation Ref:Parks 23rd edition pg 849. +/-1sd includes 68% i.e . 0.68 1SD : confidence limit = 68% 2SD : confidence limit = 95% 3SD : confidence limit = 99.7%