Unit Plan 32 (Grade 8 Math): Linear Modeling Project—From Data to Decision
8th graders design and carry out a complete data investigation—posing a question, collecting or curating data, building a scatter plot, fitting a line of best fit, and interpreting slope and intercept. They make predictions, evaluate model limits, and present clear, evidence-based findings.
Focus: Plan and carry out a small data investigation: collect or curate data, create a scatter plot, fit and interpret a line, and present findings.
Grade Level: 8
Subject Area: Mathematics (Statistics & Probability • Modeling • Functions/Algebra connections)
Total Unit Duration: 5 sessions (one week), 45–60 minutes per session
I. Introduction
This culminating project turns students into data modelers. In pairs or trios, they’ll choose a question, collect or curate a small bivariate data set, construct a scatter plot, draw an informal line of best fit, write its equation, and use it to interpret and predict—ending with a concise presentation. Emphasis: ethical and sensible data choices, clear visuals, units, responsible claims, and limits of the model.
Essential Questions
- What decision or claim can a small, well-designed linear model support?
- How do design choices (variables, units, sampling) influence the story our data tells?
- What do slope and intercept mean in context, and when are predictions trustworthy?
II. Objectives and Standards
Learning Objectives — Students will be able to…
- Plan an investigation: pose a testable question, define two numerical variables with units, and outline a sampling/curation plan (size, source, fairness).
- Construct a scatter plot with sensible scales, labels, and units; describe direction, form, strength, clusters, outliers.
- Draw an informal line of best fit, write an equation y = mx + b from two points on the line, and interpret slope and intercept in context.
- Use the line to interpolate and cautiously extrapolate; compare predicted vs actual values with qualitative error comments.
- Communicate results in a brief report or poster and a 2–3 minute presentation, including limitations and next steps.
Standards Alignment — CCSS Grade 8
- 8.SP.1: Construct and interpret scatter plots for bivariate measurement data; describe patterns of association.
- 8.SP.2: Informally fit a line and judge the fit by visual closeness; use the line to solve problems.
- 8.SP.3: Use the fitted line to solve problems; interpret slope and intercept in context.
- MP.3: Construct viable arguments and critique the reasoning of others.
- MP.4: Model with mathematics.
Success Criteria (student-friendly)
- I can make a clear, labeled scatter plot and draw a reasonable line that balances points.
- I can explain, with units, what the slope and intercept say about my situation.
- I can make and label interpolated and extrapolated predictions and say how confident I am.
- I can present a concise claim supported by the graph, numbers, and limitations.