You seem to be assuming that given you have waited for eight minutes already and that the schedule is 10 minutes that therefore half of the period remaining is

You seem to be assuming that given you have waited for eight minutes already and that the schedule is 10 minutes that therefore half of the period remaining is the expected time for the bus. That seems like a fair heuristic but I'd personally read the timetable. To get a more exact answer you also need to know the distribution of actual bus arrival times. If they turn up at your stop every 10 mins (mean) but with a standard deviation of say two minutes then your heuristic is not the best. Far more interesting is that two of the buggers will always turn up when you don't actually need one. I can prove that by assertion now and fairly confidently be able to appeal to around 60M Britons for testimony as required. This is not related to "virality" which is my newly made up term for the Lindy Effect.