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# Statistics

#### Question 3:

The following distribution shows the daily pocket allowance of children of a locality. The mean pocket allowance is Rs.18. Find the missing frequency f.

 Daily pocket allowance (in Rs) 11­ − 13 13­ − 15 15 −17 17 − 19 19 − 21 21 − 23 23 − 25 Number of workers 7 6 9 13 f 5 4

To find the class mark (xi) for each interval, the following relation is used.

Given that, mean pocket allowance,

Taking 18 as assured mean (a), di and fidi are calculated as follows.

...
 Daily pocket allowance (in Rs) Number of children fi Class mark xi di = xi − 18 fidi

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