If someone could please help with the following: underlying is $100 Expiration Jan 14 Enter custom Annual Implied vola as 50% then 1 stdev is 50% x $100 = $50. Why is Tradeking IVolatility probability calculator showing 1) plus 1 stdev price as $148.44 and minus 1 stdev price as $52.25. Should not 1 stdev price range be from $50 to $150? 2) Plus/minus 1 stdev is $52.25 and $148.44? Why is it showing the probability of touching these as 46.26% and 22.72%. Should not the probability of touching these prices be roughly equivalent, i.e. approx 68%/2 = 34%? Thanks.