To find the expected value of \( X \) for an Erlang distribution with parameters \( \lambda \) and \( n \), we use the formula:
Expected value of \( X \), \( E[X] = n ÷ \lambda \)
Where:
- \( n \) is the shape parameter of the Erlang distribution.
- \( \lambda \) is the rate parameter (reciprocal of the scale parameter).
In the Erlang distribution, \( n \) represents the number of events occurring in a given interval of time, and \( \lambda \) represents the average rate of events per unit time.
So, the expected value of \( X \) is \( \frac{n}{\lambda} \).