Mean ± 0.04 -------precision in the given case.
More is the precision, more is the safety.
Expected ± 0.04 ----accuracy.
Under precision, (a) is more precise.
If we have even numbers, the middle number is the median.
(True value-mean)*100/true value.
In the standard of deviation formula, n is the total number of measurements.
mass-- 15-20 g ---uncertain
17.43g------new weight of gold ring
M1=17.44g, m2=17.46g, m3=17.42g
Avg = (17.44+17.46+17.42)/