Suppose we use a physical balance to measure the mass of an object and find the mean value of our observations to be 156.28 g



Since we are some what uncertain, about the measurement, due to our instrument’s imperfections, we need to express this in our result. Let the least count of physical balance be 0.1 g. This implies that the uncertainty, of any measurement made with this instrument, is ± 0.1 g. Therefore, we would report the mass of this object to be (156.3 g ± 0.1 g). This implies that we can only say that the mass of the object is somewhere between 156.2 g and 156.4 g.