find the mean using direct method (marks) 10-20 20-30 30-40 40-50-50-60 60-70 70-80 (number of students) 6, 8 ,13 ,7 ,3 ,2 ,1
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Marks0 - 10 10 - 20 20 - 30 30 - 40 40 - 50 50 - 60 60 - 70 70 - 8080 - 90 90 - 100 Frequency3 5 6 7 8 9 10 12 64 Find the mean mark using step deviation ...
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sum of fi( number of students)=40
xi:class mark of 10-20=10+20/2=15
class mark of 20-30=25
class mark of 30-40=35
40-50=45
50-60=55
60-70=65
70-80=75
fixi:6×15=90
8×25=200
13×35=455
7×45=315
3×55=165
2×65=130
1×75=75
sum of fixi=1340
By direct mean method,
Mean=sum of fixi/sum of fi
= 1340/40=33.5
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