Question:
An aircraft has 120 passenger seats. The number of seats occupied during 100 flights is given in the following table.
Determine the mean number of seats occupied over the flights.
Solution:
We first, find the class mark xi, of each class and then proceed as follows.
$\therefore \quad$ Assumed mean, $a=110$,
Class width, $h=4$
and total observation, $N=100$
By assumed mean method,
$\operatorname{Mean}(\bar{x})=a+\frac{\Sigma f_{j} d_{j}}{\Sigma f_{i}}$
$=110+\left(\frac{-8}{100}\right)=110-0.08=109.92$