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in Statistics by (25.0k points)
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The marks obtained out of 50, by 102 students in a Physics test are given in the frequency table below:

 Marks (x): 15 20 22 24 25 30 33 38 45
 Frequency (f): 5 8 11 20 23 18 13 3 1

Find the average number of marks.

1 Answer

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by (26.3k points)
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Best answer

Let the assumed mean (A) = 25

 Marks (xi)  Frequency (fi) ui = xi - A = xi - 25 fiui
15 5 -10 -50
20 8 -5 -40
22 11 -3 -33
24 20 -1 -20
25 23 0 0
30 18 5 90
33 13 8 104
38 3 13 39
45 1 20 20
 N = 102 \(\sum\)fiui = 110

Average number of marks = A + \(\frac{\sum f_iu_i}{N}\)

\(=25+\frac{110}{102}=\frac{2550+110}{102}\)

\(=\frac{2660}{102}=26.08\) (approx)

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