Control Charts Using Minitab Control charts display the process average (center) and process variability (spread). Process Average is the “expectation” and Process Variability indicates “risk” associated with the expectation.

2 Frequently Used Control Charts Attribute: Go/no-go Information, sample size of 50 to 100 p-chart ( Proportion Defectives) c-chart (# Defects) u-chart (Defects/Unit) Variable: Continuous data, usually measured by the mean and standard deviation, sample size of 2 to 10 –X-bar and R-charts –X-bar and s-charts –X-charts for individuals

3 Attribute Charts in Minitab Stat / Control charts / Attribute Charts

4 p-Chart HourSampSize Non- conforming P charts are used to study the proportion of defectives in each sample. A “defective” is an attribute that makes something useless. Data on non-conforming (defective) chips produced at a facility

5 c-Chart UnitSqFtBlemishes C charts are used to display the number of defects in each sample. A defect is a flaw that is undesirable but does not make the product useless. Data are number of blemishes in 66sqft of painted area

6 U-Chart UnitSqFtBlemishesRate U charts are used to display the number of defects per unit of measurement. Useful when samples are of different sizes. Data are number of blemishes in different areas

7 Variable Charts in Minitab Stat / Control charts / Variable Charts for Subgroups or Individuals

8 XBar-R Charts SampleObs1Obs2Obs3Obs4Obs X-Bar charts are used to plot subgroup means. R charts are used to plot the range for each subgroup. Data represents actual contents in 12 oz soda cans

9 XBar-S Charts SampleObs1Obs2Obs3Obs4Obs X-Bar charts are used to plot subgroup means. S charts are used to plot the standard deviation of each subgroup.

10 Is the Process in Control? XBar-S ChartX (individual) Chart

11 Process Capability Process capability refers to the ability of a process to produce a defect-free product or service in a controlled manner of production or service environment