The mean of the following frequency distribution is 8. Find the value of p.


x



3



5



7



9



11



13



y



6



8



15



p



8



4


First draw the table as shown below;


x



f



f × x



3



6



18



5



8



40



7



15



105



9



P



9p



11



8



88



13



4



52




∑f = 41 + p



∑fx = 303 + 9p




Given mean = 8


8 =


8(41 + p) = 303 + 9p


328 + 8p = 30 + 9p


9p – 8p = 328 – 303


p = 25


So, the value of p = 25


11