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 :
`{:(,"Clock 1","Clock 2"),("Monday",12:00:05,10:15:06),("Tuesday",12:01:15,10:14:59),("Wednesday",11:59:08,10:15:18),("Thursday",12:01:50,10:15:07),("Friday",11:59:15,10:14:53),("Saturday",12:01:30,10:15:24),("Sunday",12:01:19,10:15:11):}`
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 162 s for clock 1, and 31 s for clock 2. The average reading of clock 1 is much closer to the standard time than the average reading of clock 2. The important point 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 clock 1.