An aircraft has 120 passenger seats. The number of seats occupied during 100 flights is given in the following table : Number of seats 100-104 104-108 108-112 112-116 116-120 Frequency 15 20 32 18 15 Determine the mean number of seats occupied over the flights.

 

Class Interval      Class Marks (xi)  Frequency (fi)     Deviation (di = xi – a)      fidi

100 – 104            102        15           –8           –120

104 – 108            106        20           –4           –80

108 – 112            110        32           0             0

112 – 116            114        18           4             72

116 – 120            118        15           8             120

N = Σfi = 100                      σfidi = – 8

∴ Assumed mean, a = 110

Class width, h = 4

Also, absolute perceptions, N = 100

Henceforth, discovering mean,

   

   

= 109.92

However, we realize that the seats can’t be in decimal.

In this way, the quantity of seats = 109.