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the process – Contribution of machine design, process design ining material – Typically difficult or costly to eliminate – . slight vibration in machines, slight variation in raw material, etc. Terminology (Continued) ? Importance of Variation: – Our goal is to reduce variation. – We cannot eliminate it, but we can control it. – We use statistics to quantify it and understand its causes. ? Reducing variation results in: – Predictable, controllable output. – Improved yields. – Increased profitability. Terminology (Continued) ? Variable: – Any characteristic of a person or thing. ? Quality Characteristic: – The specific variable about which information will be collected. ? Value: – Actual number that describes the quality characteristic selected as a variable. Discussion Scenarios Scenario 1 ? Due to a recent process problem, all process areas need to determine if they are running on target. At one process step, thickness measurements are recorded. 2 3 .4 1 4 5 . 0 1 2 9 . 4 1 3 8 . 8 1 1 8 . 4 7 7 .3 1 4 3 . 8 9 4 .2 1 3 8 . 6 1 2 5 . 9 1 4 0 . 3 1 2 8 . 2 3 7 .3 1 0 0 . 8 1 1 0 . 9 1 0 9 . 7 6 9 .1 1 5 9 . 3 1 1 6 . 3 1 2 1 . 9 1 2 6 . 3 1 2 3 . 0 5 9 .6 1 0 1 . 1 8 3 .9 1 3 7 . 9 1 0 6 . 8 1 0 4 . 9 1 3 8 . 1 1 0 9 . 7 1 4 9 . 4 7 9 .8 1 5 7 . 7 1 9 9 . 8 8 3 .7 3 1 0 5 . 2 1 2 8 . 5 1 1 0 . 4 1 1 3 . 3 8 2 .9 What is the quality characteristic? ? Thickness What are the values of the quality characteristic? ? , , etc. What questions would you ask to have a better understanding of the sources of variation in this data? Practice Items 1. What is variation and why do we care about it? ? Variation is the change in data value