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Sukanya Das, Lovely Professional University Unit–28: Measures of Dispersion: Standard Deviation

Unit–28: Measures of Dispersion: Standard Deviation notes

CoNteNts
objectives
introduction
28.1 Measures of Variation or Dispersion
28.2 Quartile Deviation
28.3 Coefficient of Quartile Deviation
28.4 Mean Deviation
28.5 Calculation of Mean Deviation
28.6 simple series
28.7 Discrete series
28.8 standard Deviation
28.9 Importance of Variability
28.10 summary
28.11 Keywords
28.12 review Questions
28.13 further readings

objectives

After studying this unit students will be able to:
y Understand the meaning of variation
y Know about the means of measuring variation.
y Know about the method of calculating mean deviation and standard deviation.

introduction

Variation expresses the information contained in a class of data regarding their similarity, uniqueness
and homogeneity. Using variation, we can obtain information about social activities in social research
regarding their similar and constant features. Also, we use this basis to establish a solid concept of
deviations in the information.
Variation helps increase our predictability i.e. it becomes easier to predict the future of subject of any
information. Variation helps us prevent getting distracted from certain results and saves us from
uncertain knowledge.

28.1 Measures of Variation or Dispersion

Meaning of Variation

Variation or dispersion is that quality which tells us the measure of deviation of a set of values from its
mean (or average of values). it is true that mean quantities (arithmetic mean, median, mode) does help
us to find out central theme of the complete series but is not possible to have complete and accurate

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