… But not a pattern.

Back in middle school I was taught that two points are adequate to define a line. That’s true. But when it comes to stats and collecting data, two points is far from adequate. If I collect a couple data points on some system, I can certainly calculate a line that connects the two, but I have no idea how the data I collected is impacted by random noise. The line might be a good approximation of the relationship between the two variables, but it equally may not be.

That is why you need to collect a bunch of data. It isn’t nearly as important that you can or can’t make a perfect line through all the data points. What is important is that you can understand the pattern that the data makes. Perhaps the relationship is linear, but perhaps it is somehow otherwise related. Logarithmic or exponential or seasonal patterns or something else.

While any two points may define a line, it’s not necessarily the right line.