How do I draw and determine the equation of a trend line on a scatterplot

Step-by-step explanation:

Step 1: Draw your trend line.

You begin by drawing your trend line. You want your trend line to follow your data. You want to have roughly half your data above the line and the other half below the line, like this:

trend line equation

Step 2: Locate two points on the line.

Your next step is to locate two points on the trend line. Look carefully at your trend line and look for two easy to figure out points on the line. Ideally, these are points where the trend line crosses a clearly identifiable location.

For the trend line that we just drew, we can see these two easily identifiable points.

trend line equation

We can easily identify these two points as (3, 3) and (12, 6).

Step 3: Plug these two points into the formula for slope.

The formula for slope is this one:

trend line equation

We can label our first point as (x1,y1), and our second point as (x2,y2). So our x1 is 3, our y1 is 3, our x2 is 12, and our y2 is 6. Plugging these values into the equation for slope and evaluating, we get this:

trend line equation

So our slope is 1/3.