1.

In the first proof reading of a book containing 300 pages the following distribution of misprints was obtained: No. of misprints per pages (x):012345 No. of pages (f):1549536951Find the average number of misprints per page.

Answer»

To find : the average number of misprints per page.

Use the shortcut method to find the mean of given data.For that,Let the assumed mean be (A) = 2,The deviation of values xi from assumed mean be di = xi – A.

Now to find the mean:First multiply the frequencies in column (ii) with the value of deviations in column (iii) as fidi.

 No. of misprints per pages (xi) No. of pages (fi)di = xi - A = xi - 2fidi
0154-2-308
195-1-95
23600
3919
45210
5133
 N = 300\(\sum\)fidi = -381

Now add the sum of all entries in column (iii) to obtain \(\displaystyle\sum_{i=1}^{n} f_id_i\)

and the sum of all frequencies in the column (ii) to obtain \(\displaystyle\sum_{i=1}^{n} f_id_i=N\)

So,

Average number of misprints per day = A + \(\frac{\sum f_id_i}{N}\)

where, N = total number of observations

⇒ Mean = 2 + \(\frac{-381}{300}\)

Mean = \(\frac{600-381}{300}\)

Mean = \(\frac{219}{300}\)

Mean = 0.73



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