short-term capability

**Short-term capability** is the **estimate of process potential over a limited, controlled time window with minimal drift influence** - it is useful for machine acceptance and rapid diagnostics, but should not be mistaken for lifetime process behavior. **What Is Short-term capability?** - **Definition**: Capability computed from within-subgroup variation over closely timed runs. - **Common Metrics**: Cp and Cpk based on short-window sigma estimates. - **Data Characteristics**: Back-to-back samples with stable settings, often from one tool state. - **Limitation**: Does not fully include long-term shifts from wear, environment, or operator changes. **Why Short-term capability Matters** - **Commissioning Use**: Provides rapid evidence that equipment can achieve required precision under controlled conditions. - **Debug Speed**: Helps isolate intrinsic process noise before long-term drift confounds analysis. - **Benchmarking**: Useful baseline for comparing tools or recipe alternatives. - **Control Design**: Short-term sigma informs initial control-limit and guardband setup. - **Gap Diagnosis**: Comparing short-term and long-term indices reveals hidden stability problems. **How It Is Used in Practice** - **Controlled Sampling**: Collect consecutive production or qualification runs under fixed conditions. - **Index Analysis**: Compute Cp and Cpk with clear subgroup logic and measurement-system validation. - **Follow-On Check**: Pair with long-term Ppk analysis before making release-level capability claims. Short-term capability is **an important but partial quality metric** - it shows what the process can do in a sprint, not necessarily what it will do over a season.