Don't forget you also have to divide by two (so, 1 in 24 billion) if you only want to consider the upper end of the range, since that number is essentially "fra

Don't forget you also have to divide by two (so, 1 in 24 billion) if you only want to consider the upper end of the range, since that number is essentially "fraction of the population that doesn't fall within mean +/- 6.5 stdev".