5000 would be included in the class interval 5000

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Unformatted text preview: uld be included in the class interval 5000-10000. This method is widely used in practice. b) Inclusive method: In this method, the overlapping of the class intervals is avoided. Both the lower and upper limits are included in the class interval. This type of classification may be used for a grouped frequency distribution for discrete variable like members in a family, number of workers in a factory etc., where the variable may take only integral values. It cannot be used with fractional values like age, height, weight etc. This method may be illustrated as follows: Class interval Frequency 5- 9 7 10-14 12 15-19 15 20-29 21 30-34 10 35-39 5 Total 70 Thus to decide whether to use the inclusive method or the exclusive method, it is important to determine whether the variable 55 under observation in a continuous or discrete one. In case of continuous variables, the exclusive method must be used. The inclusive method should be used in case of discrete variable. c) Open end classes: A class limit is missing either at the lower end of the first class interval or at the upper end of the last class interval or both are not specified. The necessity of open end classes arises in a number of practical situations, particularly relating to economic and medical data when there are few very high values or few very low values which are far apart from the majority of observations. The example for the open-end classes as follows : Salary Range No of workers Below 2000 7 2000 – 4000 5 4000 – 6000 6 6000 – 8000 4 8000 and 3 above 4.5 Construction of frequency table: Constructing a frequency distribution depends on the nature of the given data. Hence, the following general consideration may be borne in mind for ensuring meaningful classification of data. 1. The number of classes should preferably be between 5 and 20. However there is no rigidity about it. 2. As far as possible one should avoid values of class intervals as 3,7,11,26… .etc. preferably one should have classintervals of either five or multiples of 5 like 10,20,25,100 e...
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