In a telephone exchange , the frequency distribution of the number of telephone calls per minute for any hour are given below :

find the average number of telephone calls.

Explanation

Here, at first the following table should be prepared :

`therefore ` the average number of telephone calls `barx` , where ,
`barx=(underset(i=1)overset(9)sum)/(underset(i=1)overset(9)sum fi)=(239)/(60)=3.98` (approx)
Here , also the origin or base can be necessarily transferred ,