Propoion of area from middle of curve to +1 standard detion-: (A) 0.68, (B) 0.17, (C) 0.12, (D) 0.34
Answer is D. Ref:Parks 23rd edition pg 849. 1SD : confidence limit = 68% 2SD : confidence limit = 95% 3SD : confidence limit = 99.7% +/- 1SD: includes 68% of values, so +1SD will include half of it = 34%