A Balanced Incomplete Block Design (BIBD) is a statistical method used in experiments where not all treatments can be applied to all experimental units. In a BIBD, each treatment appears in a specific number of blocks, ensuring that every pair of treatments is compared equally across the blocks. This design helps to control variability and allows for more efficient data collection. BIBDs are particularly useful in agricultural experiments, clinical trials, and other fields where resources are limited. By using this design, researchers can obtain reliable results while minimizing the number of trials needed, making it a practical choice for many studies involving treatments and experimental units.