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2.Marks (out of 50 ) obtained in Mathematics by 100 students is given in the followingtable. Find the mean by direct methodMarksD-1010-2020-3030-4040-502010203020No ofstudents |
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Answer» Step-by-step EXPLANATION: DIRECT method size x f xf 0-10 5 20 100 10-20 15 24 360 20-30 25 40 1000 30-40 35 36 1260 40-50 45 20 900
MEAN = ∑f ∑fx
= 140 3620 =25.857 Assumed mean method size x u=x-25 f uf 0-10 5 -20 20 -400 10-20 15 -10 24 -240 20-30 25 0 40 0 30-40 35 10 36 360 40-50 45 20 20 400
mean =A+ ∑f ∑fu
=25+ 140 120 =25.875 Step DEVIATION method size x d=x-25 u=(x-25) / 10 f uf 0-10 5 -20 -2 20 -40 10-20 15 -10 -1 24 -24 20-30 25 0 0 40 0 30-40 35 10 1 36 36 40-50 45 20 2 20 40
mean =A+h× ∑f ∑fu
=25+10× 140 12 =25.875 |
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