Statistical Interpretation of Data

Abstract

It is commonplace to observe that repeated measurements of what seems to be the same object or phenomenon do not produce identical results. Measurement variation arises from a number of sources, but one root cause is often the finite precision of the measuring tool. If a simple yardstick is used to measure carpet, we expect to obtain a result no better than perhaps 1/4 inch, the smallest division on the measurement scale, but this is entirely adequate for our purpose. If we try to measure the carpet to a higher resolution, say 1/64 inch, we are likely to find that the roughness of the edge of the carpet causes uncertainty about just where the boundary really is, and measurements at different locations produce different answers. To push this particular example just a bit farther, if the measurement is performed without taking care that the ruler is perpendicular to the edges of the carpet, the measurement will be biased and the result too large.