The Folded Normal Distribution

Measurements are frequently recorded without their algebraic sign. As a consequence, the underlying distribution of measurements is replaced by a distribution of absolute measurements. When the underlying distribution is normal, the resulting distribution is called the “folded normal distribution”. The authors describe methods for estimating the mean and standard deviation of the normal distribution based on estimates of the mean and standard deviation determined from the folded normal. Tables are provided to assist in the estimation procedure and an example included.