The shop opened a second till halfway through my hour. My wait dropped by more than half, which I did not expect.
ArithmeticAnswered389 views
Counted 14 in the line, arrivals about 3 a minute, wait around 4 minutes and 40 seconds. That matched the stopwatch, which was satisfying.
Then they opened a second till onto the same line. Same arrivals. Line length dropped to 5 and my measured wait dropped to about 1 minute 20.
I expected half. I got a quarter. Have I made an arithmetic mistake or is this a real thing?
Marked as the answer
That is the pooling result and you found it a week early. Doubling servers on one line does more than halve the wait, because the second server also removes the case where one slow customer blocks everybody behind them. Week 8 is this whole lecture. Bring the numbers.
Mine did the opposite. They opened a second till with its own line and the wait barely moved, because half of us were stuck behind the person doing a return.
Two queues is not two servers. Ravi has just described the difference better than my slides do, so I am stealing it.