Step 1: Understanding the Concept:
Experimental data exhibits total variation, which is caused by both controlled experimental factors and uncontrolled random error.
Step 2: Detailed Explanation:
The statistical technique used to isolate and compare these different sources of variation is called Analysis of Variance (ANOVA).
Developed by Sir Ronald A. Fisher, ANOVA partition the Total Sum of Squares ($SS_{\text{Total}}$) into:
- Sum of Squares due to Treatments ($SS_{\text{Treatment}}$), representing the variation caused by controlled factors.
- Sum of Squares due to Error ($SS_{\text{Error}}$), representing the variation caused by random fluctuations.
This decomposition enables the computation of $F$-ratios to test whether treatment means are significantly different.
Therefore, this procedure is known as the analysis of variance.
Step 3: Final Answer
The correct option is (D).