Q7 of 141 Page 7

In the first proof reading of a book containing 300 pages the following distribution of misprints was obtained:





















No. of misprints per pages (x):



0



1



2



3



4



5



No. of pages (f):



154



95



36



9



5



1



Find the average number of misprints per page.

Let the assumed mean (A) = 2



















































No. of misprints per pages (xi)



No. of pages (fi)



ui = xi – A = xi - 2



fiui



0



154



-2



-308



1



95



-1



-95



2



36



0



0



3



9



1



9



4



5



2



10



5



1



3



3




N = 300




∑fiui = -381



Average number of misprints per day = A +


= 2 + =


= = 0.73


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5

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.

 6

The number of students absent in a class were recorded every day for 120 days and the information is given in the following frequency table:

























No. of students absent (x):



0



1



2



3



4



5



6



7



No. of days (f):



1



4



10



50



34



15



4



2



Find the mean number of students absent per day.

 8

The following distribution gives the number of accidents met by 160 workers in a factory during a month.



















No. of accidents (x):



0



1



2



3



4



No. of workers (f):



70



52



34



3



1



Find the average number of accidents per worker.

 9

Find the mean from the following frequency distribution of marks at a test in statistics:





























Marks (x):



5



10



15



20



25



30



35



40



45



50



No. of students (f):



15



50



80



76



72



45



39



9



8



6