Unformatted text preview: er of class intervals for
the frequency distributive in the whole data, we choose the lowest
and the highest of the values. The difference between them will
enable us to decide the class intervals.
Thus the number of class intervals can be fixed arbitrarily
keeping in view the nature of problem under study or it can be
53 decided with the help of Sturges’ Rule. According to him, the
number of classes can be determined by the formula
K = 1 + 3. 322 log10 N
Where N = Total number of observations
log = logarithm of the number
K = Number of class intervals.
Thus if the number of observation is 10, then the number of
class intervals is
K = 1 + 3. 322 log 10 = 4.322 ≅ 4
If 100 observations are being studied, the number of class
interval is
K = 1 + 3. 322 log 100 = 7.644 ≅ 8
and so on.
h) Size of the class interval:
Since the size of the class interval is inversely
proportional to the number of class interval in a given distribution.
The approximate value of the size (or width or magnitude) of the
class interval ‘ C’ is obtained by using sturges rule as
Range
Size of class interval = C =
Number of class interval
Range
=
1+3.322 log10 N
Where Range = Largest Value – smallest value in the distribution.
4.4 Types of class intervals: There are three methods of classifying the data according to
class intervals namely
a) Exclusive method
b) Inclusive method
c) Openend classes
a) Exclusive method:
When the class intervals are so fixed that the upper limit of
one class is the lower limit of the next class; it is known as the
exclusive method of classification. The following data are
classified on this basis.
54 Expenditure
(Rs.)
0  5000
500010000
1000015000
1500020000
2000025000
Total No. of families
60
95
122
83
40
400 It is clear that the exclusive method ensures continuity of
data as much as the upper limit of one class is the lower limit of the
next class. In the above example, there are so families whose
expenditure is between Rs.0 and Rs.4999.99. A family whose
expenditure is Rs.5000 wo...
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This note was uploaded on 01/18/2014 for the course BUS 100 taught by Professor Moshiri during the Winter '08 term at UC Riverside.
 Winter '08
 Moshiri
 Business

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