An aircraft has 120 passenger seats. The number of seats occupied during 100 flights is given in the following table.
Number of seats100−104104−108108−112112−116116−120Frequency1520321815
Determine the mean number of seats occupied over the flights.
We first, find the class mark xi of each class and then proceed as follows.
Number of seats & Class marks(xi)Frequency(fi)Deviation di=xi−afidi100−10410215−8−120104−10810620−4−80108−112a=1103200112−11611418472116−120118158120N=∑fi=100∑fidi=−8∴Assumed mean,a=110,
Class width, h = 4
and total observation, N = 100
By assumed mean method,