Std Deviation Normal Distribution. Standard deviation is a useful measure of spread for normal distributions. When a distribution is normal then 68 of it lies within 1 standard deviation 95 lies within 2 standard deviations and 99 lies with 3 standard deviations.
The standard normal distribution also called the z distribution is a special normal distribution where the mean is 0 and the standard deviation is 1. Standard deviation is a useful measure of spread for normal distributions. It shows you the percent of population.
About 95 of the values lie within two standard deviations.
Adjust the accuracy of the machine. When a distribution is normal then 68 of it lies within 1 standard deviation 95 lies within 2 standard deviations and 99 lies with 3 standard deviations. This fact is known as the 68 95 99 7 empirical rule or the 3 sigma rule. About 95 of the values lie within two standard deviations.
