The appreciation of a continuous variable

The variable is a very important aspect for any scientist’s experiment. One could easily argue that the variable is one of the cornerstones of science and statistics. It is a concept that I have been taught throughout my educational career but it is a concept that I have only started to really think about in a meaningful way. Variables are not complicated, on the surface. There are two types of variables that are commonly described: continuous and discrete. The discrete variable is a variable that has a restricted value and does not exist on a spectrum of values. The common examples that we all know would be the flip of a coin. There are only 2 outcomes from this example, either heads or tails. That is, one or the other – nothing in between. The continuous variable on the other hand, is a variable that exists in many shapes and forms and tends to be more unique when compared to the dull discrete variable. Examples of this type of variable include age, height, and time. There are many different ways to look at these variables due to them existing on a spectrum. Take height for instance. You can measure this variable down to the millimeter. But in practical use do small differences really matter? Are small changes really going to affect your experiments? This is a question I have been asking myself a lot lately as I delve into my experiments and make plans to generate quality data.

              One continuous variable I have found myself thinking about lately is time.  In my lab I do experiments to measure cytokines produced by T cells. More specifically, I study T cells in the context of HIV infection. I use a method called flow cytometry to look the expression of these cytokines. Recently, in my field a lot of work has been published to show how quickly parameters for T cells can change. Much of this work involves the application of fluidics. Fluidics allows for the ability to see changes in cells instantly. Down to the millisecond. Almost instantly cytokine production and cell phenotypes can change in response to different stimuli. Current Immunology research is focused on the general Immune response. With fluidics single cells can be precisely described. The continuous variable allows for this method to be extremely sensitive and generate the great information that a decade ago was not possible. Imagine the amount of knowledge that would be lost if we did not rely on the precision possible due to the continuous variable.