How to Graph a Residual Plot on TI-84

1. Using Built-In RESID List

This method uses the calculator’s built-in feature to make residual plots.

• STAT → 1:Edit, input x-values in L1, y-values in L2.
  
• STAT → right to CALC → select 4:LinReg(ax+b)
• Ensure it shows L1, L2, then press ENTER.
  
• STAT → 1:Edit, move to the L3
• Press 2nd → LIST → NAMES, select RESID, then ENTER to fill L3.
  
• 2nd → Y= opens Stat Plots, turn Plot1 ON.
• Set Type to scatter plot, Xlist = L1, Ylist = L3.
  
• Press ZOOM → 9:ZoomStat
• Calculator plots residuals vs. x-values.
  

2. Plotting Residuals Directly from Regression

This is a manual but useful method if loading the RESID list feels tricky.

• After LinReg(ax+b), scroll to “Store RegEQ” → Y1 → press ENTER.
  
• Go back to STAT → Edit, under L3 type:
  L2 – L1
  
• Use VARS → Y-VARS → Function → Y1, then 2nd → 1 for L1 → ENTER
  
• Same Plot setup: Xlist = L1, Ylist = L3, ZoomStat → view plot.
  

What Is a Residual Plot?

A residual plot shows the errors from a regression model, which are called residuals on a graph. Residuals are the differences between actual y-values and predicted y-values from a regression line.
A good linear model will produce residuals that are randomly scattered around zero, helping you check if the model fits well.

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