Scatter Plot Maker

Scatter Plot Maker

A best-fit line shows the overall trend of your points.

How is the best-fit line found?

This tool uses a standard method called least-squares linear regression. It finds the straight line that makes the total “vertical distance” from the points to the line as small as possible.

In other words, it chooses a slope and intercept so the line is the closest overall match to your data. This is the same basic method used in Excel, Desmos, and graphing calculators when you add a linear trend line.

Note: This tool shows the line and R² only (not confidence intervals or p-values). That keeps it simple for classroom use.

Insert Data Points

X value Y value Actions

Instructions

1. Type a graph title and axis labels.

2. Enter your X values (numbers only) and Y values in the table.

3. Add rows to add more points.

4. (Optional) Turn on “best-fit line” to show the overall trend.

5. Click “Graph Data.”

Your work auto-saves, so if your tab closes you can come back.

Key Vocabulary

Scatter Plot: a graph that shows points. Each point matches one X value and one Y value.

Trend / Best-Fit Line: a line that shows the overall pattern in the data.

Independent Variable (X): what you change or compare.

Dependent Variable (Y): what you measure.

What does R² mean?

R² (R squared) tells you how well your best-fit line matches your points.

  • If R² is close to 1, your points follow a strong straight-line pattern.
  • If R² is close to 0, a straight line does not explain the pattern very well.

“How much of the change in Y can be explained by X using this line?”

Reminder: R² does not prove that X causes Y. It only tells how well a line fits the data.