CCSS.Math.Content.HSS-ID.C.8
The standard
Compute (using technology) and interpret the correlation coefficient of a linear fit.
Common Core State Standards for Mathematics
What this standard means
Students need to use technology to find the correlation coefficient for paired numerical data, then explain what the value means. They should connect the sign to direction, positive or negative, and the size to strength, weak, moderate, or strong.
Mastery looks like reading a scatterplot, running a calculator or spreadsheet command, and saying, for example, “r = 0.82 means a strong positive linear relationship.” Students often confuse correlation with slope, think r proves causation, or describe strength using only the picture instead of the value.
Ways to teach it
- Hands-on: Give pairs a small height and arm span data set, have them enter it in Desmos or a spreadsheet, and report r.
- Prompt: Write two sentences explaining what r = -0.76 tells you about direction and strength, without using the word causes.
- Quick assessment: Show three scatterplots with r values hidden, and have students match them to 0.91, -0.64, and 0.12.
- Real-world connection: Use a sports data table, such as practice hours and free throw percentage, to compute r and discuss what it does not prove.
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Related standards
- CCSS.Math.Content.8.SP.A.3
Use the equation of a linear model to solve problems in the context of bivariate measurement data, interpreting the slope and intercept.
- CCSS.Math.Content.HSS-ID.B.6c
Fit a linear function for a scatter plot that suggests a linear association.
- CCSS.Math.Content.6.EE.C
Represent and analyze quantitative relationships between dependent and independent variables.
- CCSS.Math.Content.HSS-ID.C
Interpret linear models