Dispersion measures

Dispersion measures

1. Measures of dispersion are those in which the data in a numerical set tend to lie around a mean value. If the measure of dispersion is very low, the average is very significant for decision making.

2. The range

   • The range is the difference between the largest and smallest data in a number series.

3. The mean variance

   • The mean deviation is the average of the absolute values of the difference between each data and the arithmetic mean of the data.

4. The variance of a data set

   • The variance of a data set is the average of the squares of the differences between the data and their arithmetic mean.

5. The standard deviation

   • The standard deviation is the square root of the variance.

6. The coefficient of variation

   • The coefficient of variation is the quotient of dividing the standard deviation of a data set by its arithmetic mean and multiplying this result by 100.

7. The interquartile range

   • The interquartile range as the difference between the third quartile and the first quartile.

8. The range between 90th and 10th percentiles

   • The range between the 90th and 10th percentiles for a data series is defined as the difference between P90 and P10.

9. Bias of a distribution

   • Bias of a distribution The lack of symmetry of a distribution is called skewness, i.e. the skewness has a certain degree of asymmetry.
     • The curve in an asymmetric distribution is presented as follows:
       • (a) skewed to the right (positive skewness).
       • b) Skewed to the left (negative skewness).