Residual Plots (Regression)

Using the maize only version of eth_allrounds_final.dta with per hectare inputs:

1. Make a residual-vs-fitted plot and check for heteroskedasticity

• Run reg yield_kg fert labor i.irr i.admin_1.
• Use predict yhat to generate predicted values.
• Use predict resid, residuals to generate residuals.
• Use twoway scatter to create a scatter plot of resid against yhat with a horizontal line at zero (yline(0)).

2. Does the vertical spread of residuals change across the x-axis? What does this suggest about heteroskedasticity?

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