InterviewSolution
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InterviewSolution
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If xi' s are the midpoints of the class intervals of a grouped data, fi' s are the corresponding frequencies and \(\bar{x}\) is the mean then \(\sum{f_i(x_i - x)}\) = ?(a) 1 (b) 0 (c) -1 (d) 2 |
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Answer» Correct answer is (b)0 We know that \(\bar{x}\) = \(\cfrac{\sum f_ix_i}{\sum f_i}\) ⇒ \(\bar{x}\) Σ fi = Σ fixi … (i) Now, Σ fi (xi − \(\bar{x}\)) = Σ fixi − \(\bar{x}\)Σ fi ⇒ Σ fi (x − \(\bar{x}\)) = Σ fixi − Σ fixi [Using (i)] ⇒ Σ fi (xi − \(\bar{x}\)) = 0 |
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