Scatterplots and Correlation
Scatterplots show how two variables move together.
About this topic
A scatterplot graphs pairs of values as points to reveal whether two variables are related. An upward trend shows positive correlation, a downward trend negative, and no pattern means little or no correlation. The correlation coefficient r runs from −1 to 1, showing strength and direction.
Values of r near 1 or −1 mean the points hug a straight line, and values near 0 mean no linear relationship. Look also for outliers, clusters and curved patterns, since r only measures linear association. A strong curved pattern such as a U shape could have r near 0 even though the variables are clearly related.
Example: hours studied and exam score might have r of about 0.8, while the age of a car and its value might have r of about −0.9. Ice cream sales and drowning incidents both rise in summer, so they correlate, but ice cream does not cause drowning; hot weather is a lurking variable.
Scatterplots are used in medicine, economics and climate science. The most important lesson is that correlation does not imply causation. Always plot the data before trusting r, and check that outliers are not driving the result.
Key ideas
- Positive, negative or no correlation
- r ranges from −1 to 1
- Correlation is not causation
Quick check
Use cases: where Scatterplots and Correlation helps
- Homework: review the key idea behind Scatterplots and Correlation before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Scatterplots and Correlation without notes.
- Visual learning: play with the interactive lab to see how Scatterplots and Correlation changes when you adjust its inputs.
- Teaching a friend: explain Scatterplots and Correlation in your own words, then compare your version with the key ideas.
Number and algebra skills are used in science, engineering, budgeting and computing.
Frequently asked questions
What is Scatterplots and Correlation?
Scatterplots show how two variables move together.
What will I learn in Scatterplots and Correlation?
Positive, negative or no correlation. r ranges from −1 to 1. Correlation is not causation.
Is Scatterplots and Correlation part of Mathematics?
Yes. It is one of 200 Mathematics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Scatterplots and Correlation lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Scatterplots and Correlation?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.