There are several techniques used in quality control, including:

1. Statistical process control (SPC): SPC involves using statistical methods to monitor and control the production process. This can include monitoring key performance indicators, such as defect rates, to identify trends and patterns in the production process.
2. Inspection: Inspection involves visually inspecting products to identify any defects or quality issues. This can be done manually or using automated systems, such as machine vision systems.
3. Sampling: Sampling involves selecting a representative sample of products and inspecting them to identify any defects or quality issues. This can be done using statistical sampling methods to ensure that the sample is representative of the overall population of products.
4. Root cause analysis: Root cause analysis involves identifying the underlying causes of quality issues and implementing corrective actions to address them. This can involve using techniques such as the 5 Whys or fishbone diagrams to identify the root cause of quality issues.
5. Process improvement: Process improvement involves making changes to the production process to improve overall quality. This can include implementing best practices, such as standardized work processes or lean manufacturing techniques, to reduce waste and improve efficiency.
6. Quality audits: Quality audits involve reviewing the production process to ensure that it is compliant with quality standards and regulations. This can help to identify areas for improvement and ensure that the production process is operating at a high level of quality.