Topic: Measurement of length, mass, volume and density.?

Question

Why are several observations taken for each measurement?

Answer 1

There are sever sources of error
1. your eyes
2. The instrument you use
3. The object of measurement may not have a uniform , length, width or hight or whatever magnitude you are trying to measure.

Let's say you took a measurement of the hight of a prism

120.5mm
121.2mm
120.6mm

Average reading = 120.5+ 121.2 + 120.6)/3
Average reading =120.8 mm