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Unformatted text preview: (c) 3. (a)
15. (b) 4. (b)
12. (c) II
19. Open end n + 1
20 75th 18. 0 and negative III
36. G.M.= 45.27
37. 142.5 mm
38. Rs.14.63 39. MD= 18
44. MD=125.08; Q1=114.18; Q3=135.45
45 Mode=71.34 140 7. MEASURES OF DISPERSION –
SKEWNESS AND KURTOSIS
7.1 Introduction :
The measure of central tendency serve to locate the
center of the distribution, but they do not reveal how the items
are spread out on either side of the center. This characteristic
of a frequency distribution is commonly referred to as
dispersion. In a series all the items are not equal. There is
difference or variation among the values. The degree of
variation is evaluated by various measures of dispersion.
Small dispersion indicates high uniformity of the items, while
large dispersion indicates less uniformity.
consider the following marks of two students.
Both have got a total of 345 and an average of 69 each.
The fact is that the second student has failed in one paper.
When the averages alone are considered, the two students are
equal. But first student has less variation than second student.
Less variation is a desirable characteristic.
Characteristics of a good measure of dispersion:
An ideal measure of dispersion is expected to possess
the following properties
1.It should be rigidly defined
2. It should be based on all the items.
3. It should not be unduly affected by extreme items.
141 4. It should lend itself for algebraic manipulation.
5. It should be simple to understand and easy to
7.2 Absolute and Relative Measures :
There are two kinds of measures of dispersion, namely
1.Absolute measure of dispersion
2.Relative measure of dispersion.
Absolute measure of dispersion indicates the amount of
variation in a set of values in terms of units of observations.
For example, when rainfalls on different days are available in
mm, any absol...
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- Winter '08