Common Probability Distributions

Hi Guys, Please could someone explain the second statement… 1)Approximately 68% of the observations fall within one standard deviation of the mean. 2)Approximately 34% of the observations fall within the mean plus one standard deviation (or the mean minus one standard deviation). I can’t seem to make sense of it. Thanks

ok, got it…however why is it that the confidence interval for 1 Stdd is equal to 68% and not 90%? Thanks

Oh! Crikey!, what was i thinking, please ignore post.