Statistics & Probability

Eighth grade is where statistics stops being about computing the mean of a list and starts being about looking at two variables at once. That shift sounds small, but it changes everything. Suddenly students aren’t summarizing data — they’re hunting for relationships, drawing trend lines, writing equations that predict what hasn’t happened yet, and arguing about whether a claim is actually supported by the numbers behind it. This nine-week program covers all four 8.SP standards, with concept passages and worked examples leading into the practice.

What the Weeks Cover

Week 1 starts with scatter plots themselves — how to construct them from paired data and what a single dot on the grid actually represents. Week 2 moves into reading those plots: positive, negative, and no association; linear versus nonlinear patterns; and what an outlier or a cluster might mean in context. The vocabulary matters here, because everything later in the unit assumes it.

Weeks 3, 4, and 5 build the linear model. Week 3 introduces the line of best fit as an informal summary of a trend — drawn by eye, judged for whether it captures the data well. Week 4 puts numbers on that line: students find slope and y-intercept and write the model as y = mx + b, then interpret each coefficient in context. Slope isn’t just rise-over-run anymore; it’s dollars per hour, or miles per gallon, or pages per minute. Week 5 uses the model for prediction. Students learn the difference between interpolation, where the data range supports the answer, and extrapolation, where the model is being asked to do something it wasn’t trained on. Residuals show up as an honesty check.

Weeks 6 and 7 pivot from numerical data to categorical data. Week 6 builds two-way frequency tables from raw survey results — sorting responses into rows and columns, computing the marginal totals along the edges. Week 7 turns those counts into proportions and introduces the real question: do the row or column percentages change depending on which group you’re looking at? That’s the eighth-grade definition of association for categorical variables, and it’s surprisingly subtle.

Week 8 is about evaluating claims. Students look at scatter plots and tables drawn from real-world reporting, then look at the graphs themselves for truncated axes, cherry-picked windows, and misleading scales. The goal isn’t cynicism — it’s a habit of asking what the data actually shows before accepting what someone says it shows. Week 9 is the capstone: students integrate everything from the unit, critique flawed reasoning, and design a small statistical investigation of their own.

Five worksheets per week, full answer keys, print-ready PDF format. Aligned to Common Core 8.SP.A.1 through 8.SP.A.4.