ps. the 5th point on this site says something else. could you please clarify why to 2 d.p
http://www.cottinghams.com/david/pracs.shtml
Yeah the time you measured should be recorded to
2 d.p since the stopwatch gives values to 2 d.p
But the periodic time, it is being
calculated by averaging and you should state it to the same number of significant figures as the time recorded and not to the same d.p
Of course you can't time upto this accuracy but since it is a calculated value, you can state it to
4sf.
Marking schemes usually ask for the
same number of sf as the time recorded or one better.