strip-plot design

**Strip-Plot Design** is a **restricted randomization experimental design where two factors are applied in perpendicular strips** — one factor is applied in horizontal strips and another in vertical strips, creating a grid where each cell receives a unique combination of the two strip factors. **How Strip-Plot Design Works** - **Row Strips**: Factor A is applied to entire horizontal strips (e.g., temperature across a batch of wafers). - **Column Strips**: Factor B is applied to entire vertical strips (e.g., etch time for a group of wafers). - **Intersections**: Each row-column intersection gets a unique (A, B) combination. - **Error Structure**: Three error terms — row strip, column strip, and intersection — reflecting the randomization restrictions. **Why It Matters** - **Practical Constraints**: Reflects real fab operations where some factors cannot be independently randomized for each run. - **Efficiency**: When hardness of factor levels varies, strip-plot designs are more practical than fully randomized designs. - **Semiconductor**: Common when batch factors (furnace temperature) are crossed with per-wafer factors. **Strip-Plot Design** is **experimenting with perpendicular constraints** — a practical design for when two factors must each be applied to groups of experimental units.