Find each set's smallest and largest recorded value before comparing its spread. Equal means do not require equal ranges. Rounded times describe the display, not every hidden decimal. A small recorded spread alone does not prove accuracy or predict the next result.
Worked example
A separate set 4, 6, 5 seconds has mean 5 seconds and spans 4 to 6. Another set 5, 5, 5 has the same mean but no recorded spread. Times 4.7 and 5.3 both round to 5 seconds, so equal displays need not mean equal exact times.
Tracks R and S
These are fictional paper records; no timing experiment is required. The same cart traveled along two tracks of equal length, with the same start/stop rule and timer. Every time was recorded to the nearest whole second. Track R: 18, 20, 19 seconds. Track S: 17, 19, 21 seconds. Both sets total 57 seconds across three trials. A separate pair of readings displayed 19 seconds and 19 seconds; their unrounded values were not recorded.