<P> In statistics , the 68 -- 95 -- 99.7 rule is a shorthand used to remember the percentage of values that lie within a band around the mean in a normal distribution with a width of two , four and six standard deviations , respectively ; more accurately , 68.27 % , 95.45 % and 99.73 % of the values lie within one , two and three standard deviations of the mean , respectively . In mathematical notation , these facts can be expressed as follows , where X is an observation from a normally distributed random variable , μ is the mean of the distribution , and σ is its standard deviation : </P>
<P> In statistics , the 68 -- 95 -- 99.7 rule is a shorthand used to remember the percentage of values that lie within a band around the mean in a normal distribution with a width of two , four and six standard deviations , respectively ; more accurately , 68.27 % , 95.45 % and 99.73 % of the values lie within one , two and three standard deviations of the mean , respectively . In mathematical notation , these facts can be expressed as follows , where X is an observation from a normally distributed random variable , μ is the mean of the distribution , and σ is its standard deviation : </P>
what percent of the distribution lies within one standard deviation of the mean
what percent of the distribution lies within one standard deviation of the mean
68.27 %
68.27 %