To decide the number of class intervals for the

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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) Open-end 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 5000-10000 10000-15000 15000-20000 20000-25000 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.

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