Column

Description

Average deviation

Evaluated using the following expression:

The horizontal line in the above plot represents the average of the values in the vector.  The vertical lines represent the differences between the values of the vector and the average of the values.  The average deviation is the average difference between the vector elements and the average of the vector elements.  The sign of each element is not taken into consideration when calculating the deviation.  The sign of each element is taken into consideration when calculating the average of the elements.

Coefficient of Variation (COV)

A measure of relative dispersion given by:

The use of variation lies partly in the fact that the mean and standard deviation tend to change together in many experiments.  The higher the CoV, the higher the variability.  The lower the CoV, the less the variability of the data.  CoV is seldom of interest where the mean is likely to be near zero.

Kurtosis

Measure of flatness of a distribution.

Lower Control Limit (LCL)

Mean - 3*standard_deviation

Maximum

Maximum value indicates the largest of all output response values.

Mean

Indicates the most probable value the output response would take.

Median

The median of a scalar is that value itself.

The median of a vector with an odd number of elements is a scalar that is the element at the center of the ordered vector (element (N+1)/2, where N is the number of elements).

The median of a vector with an even number of elements is a scalar that is the average value of the two elements closest to the center of the ordered vector (elements N/2 and (N+2)/2, where N is the number of elements).

Minimum

Minimum value indicates the smallest of all output response values.

RMS

Calculates the square root of the mean of the sum of the squares of all output response values using the following equation:

Skewness

Indicates whether the probability distribution is skewed to the right or to the left.  If the skewness is zero, the probability distribution is symmetric about the mean of the distribution.  If the skewness is less than zero, the probability distribution is skewed to the left of the mean of the distribution.  If the skewness is greater than zero, the probability distribution is skewed to the right of the mean of the distribution.

Standard deviation

This is the square root of the variance.  It is a commonly used measure of dispersion.

Upper Control Limit (UCL)

Mean + 3*standard_deviation

Variance

Evaluated using the following expression: