Explanation

In regression analysis:

1. Total Sum of Squares (SST) = 3.125: This represents the total variability in the dependent variable (fetal weight).
2. Regression Sum of Squares (SSR) = 2.925: This represents the variability explained by the regression model (the relationship with weeks of gestation).
3. Residual Sum of Squares (SSE) = 0.2: This represents the variability unexplained by the model (random error).

Key relationships:

• SST = SSR + SSE
• 3.125 = 2.925 + 0.2

Interpretation:

• The variability explained by the model is SSR = 2.925
• The variability unexplained by the model is SSE = 0.2
• The total variability is SST = 3.125

Therefore, option C is correct because 2.925 represents the variability explained by the regression model.

Why other options are incorrect:

• Option A (0.2): This is the unexplained variability (residual sum of squares), not the explained variability.
• Option B (3.125): This is the total variability, not the unexplained variability.
• Option D (3.125): This is the total variability, not the explained variability.