ABSTRACT
If you count the number of students sitting in a small classroom or the number of microscopes in a laboratory, you can be certain that your numbers would be exactly correct. We would say that there is little, if any, uncertainty in your counts. However, if you were to try and count the number of grains of sand on a beach, you would be very uncertain about the exact, true number of sand grains. There are many reasons why it would be difficult to get an exact count of sand grains: it would be easy to lose some grains; it would sometimes be difficult to decide what constitutes a single grain; it would be hard to keep track of the results; and the size of the beach would constantly change due to tides and wave action. Thus, when counting small numbers of discrete items, it is possible to be certain of our counts. But when we try to count very large numbers of items, there are many possible sources of error and we become less certain that our counts are correct.
