While all non-value-added (NVA) waste should be eliminated, Lean prioritizes targeting the NVA activities that directly cause the core problem—in this case, delays and rework. These are often the most impactful ‘muda’ (waste) to remove first. Eliminating legally required steps is not an option, and trying to tackle all NVA at once is often impractical and can overwhelm the team.

A bimodal distribution in a histogram is a classic indicator that the data is coming from two different populations or processes. This suggests a specific, assignable cause of variation, such as two different machines, operators, shifts, or material batches operating with different center points. It is a clear signal that the process is not homogeneous and requires investigation to stratify the data and find the root cause.

The Reaction Plan within a Control Plan is critical for sustainability. It provides clear, pre-defined instructions for process owners on what to do when monitoring indicates the process is drifting or has become out-of-control. This institutionalizes the response, ensuring the gains are maintained by the regular workforce long after the project team has moved on. Other documents are important but do not directly address the ‘what to do if it goes wrong’ question.

If the p-value (0.03) is less than the chosen significance level alpha (0.05), we reject the null hypothesis. This means the observed data would be very unlikely if there truly was no difference between the vendor means. The correct conclusion is that there is a statistically significant difference. We cannot conclude which vendor is faster from this statement alone (that depends on the sample means), nor do we ‘accept’ the alternative hypothesis; we simply have sufficient evidence to reject the null.

The Fishbone Diagram (or Ishikawa/Cause-and-Effect Diagram) is specifically designed for this purpose. It helps a team visually structure and categorize all potential causes of a problem (the effect) into major groups (typically Methods, Machines, Materials, People, Measurement, Environment). This structured approach ensures a comprehensive exploration and organizes the brainstormed ideas for further investigation. 5 Whys is for drilling down on a single cause, a Pareto chart prioritizes, and a control chart monitors process stability.

A Two-Sample t-test is the standard hypothesis test for comparing the means of two independent groups. In this scenario, the ‘before’ and ‘after’ data sets are independent samples, and the goal is to determine if the mean cycle time after the change is significantly different from the mean before the change. One must first check if the variances of the two groups are similar to decide between the ‘equal variance’ or ‘unequal variance’ version of the test.

A SMART goal is Specific, Measurable, Achievable, Relevant, and Time-bound. ‘Increase the FCR rate from 75% to 85% within the next 6 months’ meets all criteria: It specifies the exact metric (FCR), provides a measurable baseline and target (75% to 85%), is presumably achievable, is relevant to the project, and has a clear time frame (6 months). The other options are vague and lack measurable, time-bound elements.

A Cp or Cpk value less than 1.0 indicates that the process’s natural variation (6σ) is wider than the specification tolerance. A value of 0.8 means the process spread consumes 1/0.8 = 125% of the specification window, guaranteeing a significant number of defects. Since Cpk ≈ Cp, the process is centered, ruling out a mean shift as the main issue. While measurement error could contribute, the low index primarily signals that the inherent process variation is too large.

A high %Contribution for Gage R&R (the combined repeatability and reproducibility of the measurement system) indicates that most of the observed variation in the study comes from the measurement tool and its use, not from actual differences between the parts. This means the gauge is not precise enough to reliably detect the true process variation; the ‘noise’ of measurement is drowning out the ‘signal’ of part differences. The system must be improved before meaningful process data can be collected.

While all non-value-added (NVA) waste should be eliminated, Lean prioritizes targeting the NVA activities that directly cause the core problem—in this case, delays and rework. These are often the most impactful ‘muda’ (waste) to remove first. Eliminating legally required steps is not an option, and trying to tackle all NVA at once is often impractical and can overwhelm the team.0