Course Objectives

Important University Policies

Class Time and Place

Prerequisites

Blackboard

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This page is the general description of the course and suggested expectations for both the student and the expectations of the teacher.

Measures of Dispersion

Formated version of this page for printing

Measures of dispersion are used to describe the amount of scatter around the center of the distribution. They include range, mean deviation, variance, standard deviation, and coefficient of variation.

Range

This is simple the difference between the largest value and the smallest value.

Mean deviation

This is the mean absolute difference of each observation and averaged.

Variance

The formula for the populations is different that the formula for the sample.

Population variance is calculated as follows:

Sample variance is estimated as follows:

Computer Formulation

The formulations are much easier to use when calculating the these on a computer or calculator.

Standard Deviation

The standard deviation is the square root of the variance. The population standard deviation can be calculated as follows:

The sample standard deviation can be calculated as:

Coefficient of Variation

Standard Error

 

Also See:

Phillips, J. L. 2000. How to think about statistics. W. H. Freeman and Co. New York. 202 pp. ISBN 0-7167-3654-3

Chapter 4 - Measure of Dispersion and Variability pages 27-32 in:

Zar, J. H. 1984. Biostatistical Analysis. Prentice-Hall, Inc. Englewood Cliffs, New Jersey. 718 pp.