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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. Frequently Used Control Charts.
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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.
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
Attribute Charts in Minitab Stat / Control charts / Attribute Charts
p-Chart P charts are used to study the proportion of defectives in each sample. A “defective” is an attribute that makes something useless.
c-Chart 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.
U-Chart U charts are used to display the number of defects per unit of measurement. Useful when samples are of different sizes.
Variable Charts in Minitab Stat / Control charts / Variable Charts for Subgroups or Individuals
XBar-R Charts 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
XBar-S Charts X-Bar charts are used to plot subgroup means. S charts are used to plot the standard deviation of each subgroup.
Is the Process in Control? XBar-S Chart X (individual) Chart
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