To calculate the 95% confidence interval for the DB coefficient, we use the formula: $\text{CI} = \hat{\beta} \pm t_{critical} \times \text{SE}(\hat{\beta})$

Given values:

• Estimated coefficient ($\hat{\beta}$) for DB = 0.27
• Standard error ($\text{SE}$) for DB = 0.029
• Number of observations ($n$) = 43
• Number of independent variables ($k$) = 2

The degrees of freedom (df) are calculated as: $df = n - k - 1 = 43 - 2 - 1 = 40$

For a 95% confidence interval and $df = 40$, the critical $t$-value is approximately 2.021. Calculating the margin of error: $\text{ME} = 2.021 \times 0.029 \approx 0.0586$

The confidence interval is: $`$0.27` \pm 0.0586 = (0.2114, 0.3286) $$ This matches Option D.