## "Building" the Cumulative Density Function from the Probability Density Function

Some political science students struggle with making the mental connection between the probability density function (PDF) and the cumulative density function (CDF). But understanding how each of them work, and how they are connected, is essential for understanding many topics in quantitative political science research, from p-values to logit distributions and plenty besides. This pseudo-animated graphic, created in R, shows how you can think about intervals within the PDF as "blocks" and the CDF as being constructed by moving and stacking blocks from left to right, using a normal distribution of Americans' heights as an example. (You can edit the code within the console, so see what happens as the interval in the sequence shrinks below 1.)