For a standard normal distribution, find the percentage data that are more the 2 standard deviations below the mean or more than 3 stander deviations above the mean. Solution it might also help to know the bell-shape and the symmetry of the normal distribution normal distribution is symmetric so: percent of data above 2 standard deviation = percent of data below 2 standard deviation = roughly 2.5% more than 3 standard deviations is roughly 0.2% The exact percentages will depend on which graph you are looking at because the numbers gathered uses numerial methods (so some numbers are \"more exact\" than others, the wiki link below has a rough estimate). You should also know that within two standard deviations from the mean covers 95% of the data..