Fit the Line for teachers

Fit the Line is a free game for practicing the line of best fit. Run it live with your class using a four-letter code, or let students play on their own. Students never need an account.

What students practice

Judging a linear trend in a scatter plot and placing a line by eye.
Comparing their line to the least-squares regression line, with both equations shown.
Residuals and the sum of squared residuals (SSE), including drawing the residuals for either line.
The correlation coefficient r and what it says about how tightly the dots follow a line.
How stray points can pull a regression line, on the Hard setting.

Related standards

The game connects closely to these Common Core State Standards for Mathematics. Check your own state's standards for exact wording and numbering.

8.SP.A.2: informally fit a straight line to a scatter plot and judge the fit.
HSS-ID.B.6: represent two-variable data on a scatter plot, fit a function and assess the fit, including residuals.
HSS-ID.C.7 and C.8: interpret the slope and intercept of a linear model, and compute and interpret the correlation coefficient.

Running a class game

Open fittheline.com on the teacher computer and press Launch a class game. No login is needed.
Choose a difficulty and a number of rounds (5, 10 or 15), then press Create. Show the four-letter code on the board.
Students open fittheline.com on any device, press Join a class, and enter the code and their first name or a nickname. Names appear in your lobby, and you can remove a name with the x. If you turned on Fun names, students leave the name box blank and each gets a random animal name such as Sassy Squirrel.
Press Start game. Everyone sees the same dots in each round and locks in a line.
When students have locked in, press Reveal. You see all of the students' lines, the true line and the standings. Talk through the result, then press Next round.
At the end the class gets a podium. You can download the scores as a CSV file. Pressing End class deletes the class and every name.

Discussion prompts for the reveal

Before you reveal, ask: do you expect more students to land above or below the true line?
After you reveal, ask: what did the best lines do that the others did not?
Which dots would change the line most if you moved them? Why do stray points pull harder?
On the residuals view, which line has the smaller sum of squared residuals, and by how much?
What does r tell us about this round? Would a better line always be possible if r were close to 1?

Ways to use it

Warm-up: a 5-round class game at the start of a lesson on regression.
Full lesson: a 10-round game with a short discussion after each reveal.
Practice or homework: solo play, where students try to beat their own best average.
Differentiation: Easy for a first look at scatter plots, Hard for students ready to discuss outliers and influence.

Questions

Is it free?: Yes. There are no ads and no subscriptions.
Do students need accounts?: No. Students enter a class code and a name.
What devices work?: Any device with a modern web browser and an internet connection, including phones, tablets, Chromebooks and computers.
What is collected?: For class games, only the name a student types, their lines, and a random anonymous ID, deleted when you end the class. Read the full privacy policy. Please ask students to use first names or nicknames.
Is my school's web filter going to block it?: Some filters block new websites at first. If fittheline.com does not load for students, ask your school's technology staff to allow it.
Something is not working or I have a request.: Email [email protected].

Launch a class How to play