1. Problem 3.1

2. Plot of raw data

3. R-chart

4. What about subgroup 8? Raw data indicates a possible outlier. May also be isolated special cause. Check measurement system. Check production conditions at time and location of observation.

5. X-bar chart

6. What about subgroups 4,7 and 12?

7. What’s possible. Subgroups 4 and 7 don’t show a lot of variability. Check production conditions for those subgroups. Subgroups 12 is marginal and there was more variability in that data. Maybe false signal, maybe not.