Adjusted R2 F Statistic 596De6
1. **State the problem:**
We are given a regression model with sample size $n=8$, $R^2=0.937$, and an ANOVA table. We need to find the adjusted $R^2$ (denoted $\bar{R}^2$) and the F-statistic for the model.
2. **Recall formulas:**
- Adjusted $R^2$ is calculated by:
$$\bar{R}^2 = 1 - \frac{(1-R^2)(n-1)}{n-p-1}$$
where $p$ is the number of predictors (excluding intercept).
- The F-statistic for the model is:
$$F = \frac{MS_{Regression}}{MS_{Residual}}$$
where $MS$ is mean square.
3. **Identify values:**
- $R^2 = 0.937$
- $n = 8$
- From the ANOVA table, Regression degrees of freedom $DF_{Regression} = 2$ (so $p=2$ predictors)
- $MS_{Regression} = 10.5128$
- $MS_{Residual} = 0.2846$
4. **Calculate adjusted $R^2$:**
$$\bar{R}^2 = 1 - \frac{(1-0.937)(8-1)}{8-2-1} = 1 - \frac{0.063 \times 7}{5} = 1 - \frac{0.441}{5} = 1 - 0.0882 = 0.9118$$
Rounded to three decimals: $\bar{R}^2 = 0.912$
5. **Calculate F-statistic:**
$$F = \frac{10.5128}{0.2846} \approx 36.93$$
6. **Interpretation:**
- The adjusted $R^2$ accounts for the number of predictors and sample size, slightly lower than $R^2$.
- The F-statistic tests if the model explains a significant amount of variation compared to residual error.
**Final answers:**
- Adjusted $R^2 = 0.912$
- $F = 36.93$