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DA0-002 Data Analysis Practice Question

A data analyst uses linear regression to model the relationship between advertising spend and sales. The residual plot shows a clear U-shaped pattern. What assumption is violated?

⚠ Common exam trap

CompTIA often tests the distinction between residual pattern shapes and their corresponding assumptions, so the trap here is that candidates confuse a curved pattern (nonlinearity) with heteroscedasticity or non-normality, leading them to pick B or C instead of D.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Linearity

The U-shaped pattern in the residual plot indicates that the relationship between advertising spend and sales is not linear; the model fails to capture the curvature in the data. Linear regression assumes a straight-line relationship between predictors and the response, so a systematic pattern like a U-shape directly violates the linearity assumption. This means the model is misspecified and requires a transformation or a nonlinear modeling approach.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Independence of residuals

    Why it's wrong here

    Independence violations appear as autocorrelation in time series, not a pattern in residuals vs fitted.

  • Homoscedasticity

    Why it's wrong here

    Homoscedasticity violations show increasing/decreasing spread, not a U-shape.

  • Normality of residuals

    Why it's wrong here

    Normality is assessed via histogram or Q-Q plot, not residual vs fitted plot.

  • Linearity

    Why this is correct

    A U-shaped pattern means the relationship is not linear; the model is missing a nonlinear term.

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Last reviewed: Jun 30, 2026

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