Find the mean of the following frequency distribution:


Class



1 - 3



3 - 5



5 - 7



7 - 9



Frequency



9



22



27



18


For equal class intervals, we will solve by finding mid points of these classes using direct method.


CLASS



MID - POINT(xi)



FREQUENCY(fi)



fixi



1 - 3



2



9



18



3 - 5



4



22



88



5 - 7



6



27



162



7 - 9



8



18



144



TOTAL




76



412




We have got


Σfi = 76 & Σfixi = 412


mean is given by





Thus, mean is 5.421


9