= Normal Distribution = The '''normal distribution''' is a bell-shaped continuous probability distribution that is parameterized to a mean and standard deviation. <> ---- == Description == The distribution is bell-shaped. * 68.27% of the cumulative distribution is within 1 standard deviation of the mean * 95.45% within 2 * 99.73% within 3 ---- == Statistics == The mean and standard deviation are necessarily given by the distribution formulation. ---- == Usage == === Standard Normal Distribution === The normal distribution characterized by a mean of 0 and a standard deviation of 1 is called the '''standard normal distribution'''. This distribution is referenced for '''Z scores''' (alternatively called '''Z statistics'''). As an example, for a two-tailed test and a [[Statistics/TestStatistic|significance level]] of 5%, the critical Z score value is 1.96. ---- CategoryRicottone