Run Chart
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Stat > Quality Tools > Run Chart

Use Run Chart to look for evidence of patterns in your process data, and perform two tests for non-random behavior. Run Chart plots all of the individual observations versus the subgroup number, and draws a horizontal reference line at the median. When the subgroup size is greater than one, Run Chart also plots the subgroup means or medians and connects them with a line.

The two tests for nonrandom behavior detect trends, oscillation, mixtures, and clustering in your data. Such patterns suggest that the variation observed is due to special causes - causes arising from outside the system that can be corrected. Common cause variation is variation that is inherent or a natural part of the process. A process is in control when only common causes affect the process output.

Dialog box items

Data are arranged as

Single column: Choose if data is in one column. Enter a column.

Subgroup size (use a constant or an ID column): Enter the subgroup size (for equally sized subgroups) or a column of subscripts (for unequally sized subgroups).

Subgroups across rows of: Choose if subgroups are arranged in rows across several columns. Enter the columns.

For data in subgroups  You can plot either the subgroup means or medians as points on the graph. Minitab uses the points to count the number of runs in tests for randomness.

Plot subgroup means: Choose to plot the subgroup means as points on the graph.

Plot subgroup medians: Choose to plot the subgroup medians as points on the graph.

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