Two clocks are being tested against a standard clock located in a national laboratory. At 12:00:00 noon by the standard clock, the readings of the two clocks are :

If you are doing an experiment that requires 'precision time interval' measurements , which of the two clocks will you prefer ?

Explanation

The range of variation over the seven days of observations is 164s for clock 1, and 32 s for clock 2, the average reading of sclock 1 is much closer to the standard time than the average reading of clock 2.
The important pont is that a clock is zero error is not as significant for precision work as its variation, because a .zero-error. can always be easily corrected . Hence clock 2 is to be preferred to clock1.