Measure Phase

Goal or purpose:

• To document the existing process (SIPOC, flowchart, fishbone diagram, value stream map).
• To establish techniques for collecting data.
• To ensure the performance of the needed measurement systems (Accuracy, Precision, Repeatability, Reproducibility, Stability, Linearity, Discrimination)
• To collect the data.
• To establish a baseline, including confirmation of financial considerations.
• To display the data graphically so project opportunities may be highlighted.
• To focus the project's effort by gathering information on the current situation.

Deliverables:

• A more focused problem statement.
• A detailed process map.
• A fishbone diagram and a failure mode and effects analysis (FMEA).
• A data collection plan with designations on the process map.
• A list of measurements to validate.
• A validated measurement system including gauge repeatability and reproducibility.
• Sufficient data for the analysis phase.
• A complete graphical analysis, including a Pareto chart, trend charts, box plots, histograms and scatter plots.
• Baseline primary and secondary metrics indicated on a trend chart.
• A baseline capability study, including calculation of the sigma levels.

Relevant tools:

• Process mapping (SIPOC, flowchart, fishbone diagram, value stream map).
• Data collection tools such as check sheets, forms and concentration diagrams.
• Cause and effect matrices, flow charts, FMEA and gauge R&R.
• Graphical techniques such as Pareto charts, time plots, control charts and histograms.
• Process sigma calculations.

• Change management tools.

Questions to be answered:

• What is the current status of the situation?
• What problem or gap are you addressing? Where, when and how often does the problem occur? How severe is it?
• What data are you collecting? How will you collect it? How can you ensure your data collection process is reliable and valid?
• What does your collected data tell you about the problem or gap?
• How did you define defect, unit and opportunity?
• What is the current process capability?
• Have you found any quick improvements? What is your plan for implementing them? Will this affect the business case? Given your understanding of the problem or gap, do you need to change the charter?
• Have you completed a measurement error study? What are the results? Do you need better gauges? What would be the cost?
• Have you completed a process map (flowchart)? Who was involved in its development?

Measurement System Analysis

Everything we know about a measured attribute comes via a measurement system. We can study and control the quality of that measurement system.

Bias (Accuracy) The difference between the average measured value and the agreed-upon standard. Bias is controlled by calibration. Bias is sometimes termed accuracy. Imagine a bulls-eye. It is the cluster of shots centered off of the middle.

Repeatability The variation in measurements obtained with one instrument when used several times by one technician while measuring the identical characteristic on the same part.

Reproducibility The variation in measurements obtained by different technicians with one instrument while measuring the identical characteristic on the same part.

Precision Repeatability and reproducibility combine to give precision. Precision is the amount of variation in the measurements not due to what you are measuring varying but due to the measurement system. Imagine a bulls-eye target. It is the spread of the cluster of shots.

Stability Measurement stability is the change in bias over time.

Linearity The difference in bias measurements through the expected range of the gauge.

Discrimination Sometimes called resolution. It is the ability of the measurement system to divide measurements into fine-enough categories to meaningful to the purpose for the measurements.

Measure Phase 1. A fishbone diagram 2. A data collection plan 3. A list of measurements to validate Measure Phase 1. A fishbone diagram 2. A data collection plan 3. A list of measurements to validate