Three measurements of the time for 20 oscillations of a pendulum give `t_1 = 39.6s, t_2 39.9s and t_3 = 39.5s . The precision in the measurement is

Explanation

No. of oscillations = 20
`t_(1)=39.6 sec, t_(2)=39.9 sec, t_(3)=39.5sec`
`" "`Mean value `=(t_(1)+t_(2)+t_(3))/3=(39.6+39.9+39.5)/3=119/3=39.66`
`" "`Mean vlaue = 39.7 sec, Precision = 0.1 sec.
Accuracy is the closeness of measured value with true value.
Hence 39.6 is accuracy.