Data Analysis
Lessons in this chapter
About Data Analysis
Data Analysis extends earlier grades' single-variable data work to relationships between two variables, both numerical and categorical.
Scatter Plots has kids plot pairs of related values and look for a pattern, while Lines of Fit has them draw (and later, use) a single line that best approximates that pattern, making it possible to estimate one value from the other.
Two-Way Tables organizes data on two categorical variables at once, like favorite subject by grade level, so relationships between categories can be read directly from the table.
Choosing a Data Display closes the chapter by having kids match a real dataset to the display that represents it best: scatter plot, two-way table, or one of the displays from earlier grades, based on whether the data is numerical or categorical, and whether it involves one variable or two.
Each of the four lessons is an 8th grade math worksheet worked inside the page: Scatter Plots, Lines of Fit and Two-Way Tables give your child real data to plot, read and interpret rather than finished charts to look at. Marking happens per question, so a value read off the wrong axis is corrected on the spot. All four are free to try, with no login needed for your first 3.
Frequently asked questions
Scatter Plots has your child plot pairs of related values and describe the pattern, positive, negative or none at all. Lines of Fit then draws a single line approximating that pattern and uses it to estimate one value from another. Two-Way Tables organizes data on two categorical variables at once, and Choosing a Data Display closes by matching a real data set to the display that represents it best. This sits in the Common Core domain Statistics and Probability (8.SP).
A scatter plot plots pairs of related numerical values as points, letting a viewer see whether the two variables have a pattern, like a general upward trend, a downward trend, or no clear relationship at all.
A line of fit is a single straight line drawn to best approximate the pattern in a scatter plot, and once drawn, it can be used to estimate a y-value for an x-value that wasn't actually in the original data.
A two-way table organizes data on two categorical variables at once: for example, favorite subject (rows) by grade level (columns), so the count for any specific combination can be read directly where its row and column meet.
Use a scatter plot when both variables are numerical (height and weight, for instance); use a two-way table when at least one variable is categorical (favorite subject, yes/no answers).
Drawing a line that passes through every single point exactly, rather than a single line that reasonably balances being close to all the points overall: a line of fit is an approximation, not a connect-the-dots exercise.