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200 UNIT VII: STATISTICAL TOOLS AND INTERPRETATION, 25th item falls in the group 4-6, hence median class is 4-6, L =4, c.f 20, f=10, i=2, %3D, 2., M = L, +, 5x 2, 25 20, 4+, = 4 +1=5, * Median =5, 9.3.2, Calculation of Median in a Mid-value Series, intervals are to be formed (method discussed in section 4.6.3 of chanter, Once a regular series is obtained, further steps to calculate median ar, earlier (section 9.2.3)., ILLUSTRATION 11 Compute median from following data :, Marks (mid-value), 15, 25, 35, 45, 5., Number of students, 12, 11, 8., 6., Solution. First we will find class intervals using mid-values, Marks (X), Number of students (f), 0-10, 10-20, 12, 22 c.f., 20-30 Median class, 30, 30-40, 11, 40-50, 6., N = Ef = 50, 50, Here N = 50, M = Size of, th item, = Size of, 50, th item = Size of 25th item, %3D, %3D, 25th item falls in the group 20-30, hence median class is 20-30, L= 20, c.f = 22, f = 8, i 10, %3D, M= L, + 2, 25-22, 3D20+, x 10 = 20 +, 30 - 20 + 3.75 = 23.75, 8., Median marks = 23.75, 8., STATISTICS FOR ECONOMICS-XI