skewreduction.m- skewness reduction (transformation method)

Data transformation technique to reduce skewness of non-normal data. (nonnormal data to normal data)

Skewness Reduction

USAGE: [xt r sk]=skewreduction(x)

Input:
x: original data (skewed data) - x should be positive. If some of the observations are negative the following transformation can be used before skewness reduction x=x-min(x)

Outputs:
xt: transformed data (data with skewness close to 0)
r: a root in which xt=x.^r
sk: skewness of transfomed data

This function tranform x (a skewed data) to xt in which xt has skewness close to zero. This is useful to trasform skewed (non-normal) data to normal (or close to normal)data.

Example 1 (x has positive skewness):
x=gamrnd(1,4,1,1000);
[xt r sk]=skewreduction(x)

Example 2 (x has negative skewness):
x=wblrnd(3,20,1,1000);
[xt r sk]=skewreduction(x)
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Copyright(c) Babak Abbasi, RMIT University, 2011

References:

1-Niaki, S.T.A and Abbasi, B., 2007, Skewness Reduction Approach in Multi-Attribute Process Monitoring
Communications in Statistics - Theory and Methods Volume 36, Issue 12, 2007

2- Hosseinifard S.Z., Abbasi B., Ahmad S., Abdollahian M., 2009, A transformation technique to estimate the process capability index for non-normal processes , International Journal of Advanced Manufacturing Technology 40 (5-6), 512-517.