As National Weather Service survey teams scouted more storm-damaged areas after Sunday’s severe weather, the tally of tornado touchdowns just keeps rising. So far, the NWS has confirmed 9 twisters ...

Tallies are useful as it is very clear to see ... It would be sensible to group the data in class intervals of 5, so 0–4, 5–9, 10–14, 15–19 and so on. When grouping data, it is important ...