🟪 1-Minute Summary

ANOVA (Analysis of Variance) tests if means of 3+ groups are significantly different. Instead of multiple t-tests (which inflates Type I error), ANOVA does one omnibus test by comparing variance between groups to variance within groups. If significant, use post-hoc tests to find which specific groups differ. One-way ANOVA has one factor; two-way has two factors.


🟦 Core Notes (Must-Know)

What is ANOVA?

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One-Way ANOVA

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Two-Way ANOVA

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How ANOVA Works

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F-statistic in ANOVA

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Post-Hoc Tests

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Assumptions

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🟨 Interview Triggers (What Interviewers Actually Test)

Common Interview Questions

  1. “Why use ANOVA instead of multiple t-tests?”

    • [Answer: Multiple t-tests inflate Type I error (α)]
  2. “ANOVA is significant. What do you do next?”

    • [Answer: Post-hoc tests like Tukey’s HSD to find which groups differ]
  3. “What does the F-statistic represent in ANOVA?”

    • [Answer: Ratio of between-group variance to within-group variance]

🟥 Common Mistakes (Traps to Avoid)

Mistake 1: Using ANOVA for 2 groups

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Mistake 2: Not checking assumptions

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Mistake 3: Stopping after significant ANOVA

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🟩 Mini Example (Quick Application)

Scenario

[Comparing website conversion rates across 4 page designs]

Solution

from scipy import stats

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