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Our Process

Our Process. Tower. Elevation. Arm. Front. Back. Operational Definition. Need two things: a method of measurement or test a set of criteria for judgment For example, what are operational definitions for the following: on-time delivery good service 50% wool blanket.

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Our Process

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  1. Our Process Tower Elevation Arm Front Back

  2. Operational Definition • Need two things: • a method of measurement or test • a set of criteria for judgment • For example, what are operational definitions for the following: • on-time delivery • good service • 50% wool blanket source: Moen, Nolan and Provost, Improving Quality Through Planned Experimentation

  3. Data Collection • Collect 5 data points for each team member • Plot run chart (use chart wizard) • Construct a histogram (Data | Data Analysis | Histogram) • Construct a box and whiskers plot (use box&whiskers.xls) • Calculate x-bar and s (Data | Data Analysis | Descriptive Statistics) • Discuss results and be prepared to brief results to other groups

  4. Data | Data Analysis Descriptive Statistics Histogram

  5. Insert | Line Chart Box and Whiskers XLS

  6. What the Exercise Statistics Reveal • The sample mean (x-bar) describes typical distances in one number. • Other measures of central tendency include: median and mode. • The sample standard deviation (s) provides a measure of the ‘average’ deviation around the mean.

  7. Using x-bar and s • The empirical rule assumes the underlying distribution is normal: • 68% within ± 1 s • 95% within ± 2 s • 99 % within ±3 s • For any distribution: • At least 75% within ± 2 s • At least 89% within ± 3 s

  8. Histograms • Shows the distribution of process outcomes. • Look for center, shape and spread • Compare to: • your expectations and knowledge • target and specification requirements • across shifts, operators, machines, etc

  9. Process capability EXCEL: =Normdist(x, mean, std dev, 1) to calculate percent non-conforming material.

  10. X-3sA X X-1sA X-2sA X+3sA X-6sB X X+6sB X+2s X+1sA • Estimate standard deviation: • Look at standard deviation relative to specification limits • Don’t confuse control limits with specification limits: a process can be out of control, yet be incapable = / d s ˆ R 2 The Statistical Meaning of Six Sigma Process capability measure Upper Specification Limit (USL) Lower Specification Limit (LSL) Process A (with st. dev sA) x Cp P{defect}ppm 1 0.33 0.317 317,000 2 0.67 0.0455 45,500 3 1.00 0.0027 2,700 4 1.33 0.0001 63 5 1.67 0.0000006 0,6 6 2.00 2x10-9 0,00 3 Process B (with st. dev sB)

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