What is a scatterplot?

1 Answer
Sep 10, 2014

A scatterplot is simply a graph with random coordinates on it.

When we're working with real life data, we often find that it is (to be informal) quite random. Unlike with the data you usually receive in math problems, you don't have any exact trend to it, and can't document it with a single equation like #y = 2x+4#. For example, consider the graph below:


If you notice, the points don't have an exact trend which they follow. For example, some points have the same #x# value (hours studied) but different #y# values (regents scores).

It is in these kinds of situations that you would use a scatterplot. Rather than deriving equations and drawing lines straight away, you would simply plot all your given coordinates on your graph. Why is this useful? Well, you can use this then to make an approximation as to how the data is behaving.

For example, in the above graph you see that all the points seem to be sloping upwards as the number hours of study increases. Therefore, you could infer that as the number of hours of study increases, so do the Regents Scores. Again, this may not be 100% accurate, but it's a strong estimate.

Lastly, you can use this to derive what is called a best fit line. Best fit lines basically are lines that go as close to all the data points as possible. It does not need to touch any of the data points themselves, but needs to go as close to all of them as possible. TI-83 and 84 calculators can find you the equation of your given stat plot for you. This video explains how you can do that:

How to find best fit lines in TI-83 or 84 calculators

Hope that helps :)