Question

If the mean of the following data is 50, find the missing frequency “ f ”
Class interval 0-20 20-40 40-60 60-80 80-100
frequency 17 f 32 24 19

Answer 1

Answer:

Mid Value =(lower class interval+higher class interval) /2

class interval Frequency(f) Mid value(x) fx

0-20 17 10 170

20-40 f 30 30f

40-60 32 50 1600

60-80 24 70 1680

80-100 19. 90 1710 Total N=92+f. €fx=5160+30f

Mean= €fx

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N

or, 50=5160+30f

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92+f

or, 50(92+f)=5160+30f

or, 4600+50f=5160 +30f

or, 50f-30f=5160-4600

or, 20f=560

or, f = 560

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20

f=28

Therefore,the missing 'f' is 28.