Little's Law wants one arrival rate. My queue has four, depending on what time I stand there. Which one goes in the formula?
ArithmeticAnswered556 views
Counted the till for an hour. Arrivals per minute went 1.2, then 3.8, then 2.1, then 6.4 when a bus emptied out.
If I average those I get 3.4, which describes no ten minutes of that hour. If I use the busy one I get a wait that most people never had.
Which number is the one the formula wants?
Marked as the answer
None of them, and that is the useful answer. Little's Law holds over a period where the queue is not growing without bound, so pick a window where the rate is roughly flat and do the arithmetic inside it. Four windows, four sums. The four answers are your week 3 result and they are more interesting than one average would have been.
So I am not doing it wrong, I am doing it four times.
Yes. And when you write it up, say which window you would staff for. That is the question the whole course is asking.