Analysis of Variance(KA/SAP/U16AnalysisOfVariance)
Unit 16: Analysis of Variance (ANOVA)
1. What is ANOVA?
Analysis of Variance (ANOVA) is a statistical method used to compare the means of three or more groups to determine if at least one group mean is different from the others. It helps answer questions like: "Do different teaching methods lead to different average test scores?"
2. Types of ANOVA
- One-way ANOVA: Compares means across one factor (e.g., test scores by teaching method).
- Two-way ANOVA: Compares means across two factors (e.g., test scores by teaching method and gender).
3. Assumptions of ANOVA
- Independence of observations
- Normality (data in each group are approximately normal)
- Homogeneity of variances (each group has similar variance)
4. The ANOVA Table and F-statistic
ANOVA uses the F-statistic to compare the variance between group means to the variance within groups. The ANOVA table summarizes the calculations:
Source | Sum of Squares | df | Mean Square | F |
---|---|---|---|---|
Between Groups | SSbetween | k-1 | MSbetween | F = MSbetween / MSwithin |
Within Groups | SSwithin | N-k | MSwithin |
5. Interpreting ANOVA Results
If the F-statistic is large and the p-value is small (typically < 0.05), we reject the null hypothesis and conclude that at least one group mean is different.
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