If you were to measure the length of your hand down to the smallest unit of measurement on your standard ruler, the millimeter, it is likely that you would not get the same measurement every single time. This is not really just the case with very small units of measurement; in general, if you, the human, measure the same item repeatedly, you are bound to have some differences or uncertainties with an increasing number of measurements made. You might call this experimental error (Ebbing and Gammon 2009). In science, and not just in chemistry, this must be accounted for accordingly.
One of the many things that really stuck in my head in my introductory chemistry course, the first semester, was the difference between precision and accuracy. I was actually tested on this conceptually many, many times, in both the lecture course and in the laboratory. Trust me when I say that knowing the difference between precision and accuracy is as important a concept as one gets. While I’ve mentioned that chemistry is a quantitative subject, do not turn a blind eye to information that appears meaningless simply because it is conceptual.
The most important thing to take away from this post is the definition of precision, the definition of accuracy, and how they differ. Precision refers to how close a set of values obtained from identical measurements of a quantity is. For example, if you measure the length of an Amazonian giant centipede six times and get the measurements 30 cm, 29 cm, 30 cm, 30 cm, 31 cm, and 30 cm, you would be said to have high precision in your measurement of the centipede. Accuracy, then, refers to how close a single measurement is to its true value. Say that you are measuring the length of the same centipede with a known value of 30 cm. If, after performing your own measurement, you get a value of 23 cm, you have not measured very accurately (Ebbing and Gammon 2009).
Originally, I wanted to combine this post with a discussion on significant figures, but I thought that this concept was important enough on its own that you might find it worth understanding thoroughly. And, the discussion significant figures will be a bit more lengthy (and equally as important), so I’ve decided to leave it for the next post.
A prospective medical student, looking to help others succeed.