Quality Control Charts for Variable Lists - Attributes Tab

Select the Attribute tab of the Quality Control Charts for Variable Lists Startup Panel to access the options described here.

C chart for attributes

Select C chart for attributes and click the OK button in the Startup Panel to begin this analysis (you can also double-click C chart for attributes to start the analysis). In these charts, we plot the numbers of defectives and it is constructed based on the Poisson Distribution, which is also referred to as the distribution of rare events.

U chart for attributes

Select U chart for attributes and click the OK button in the Startup Panel to begin this analysis. In these charts, we plot the rates of defectives, that is, the numbers of defectives divided by the number of units inspected. Like the C chart, this type of chart is based on the Poisson distribution, but unlike the C chart, this chart does not require a constant number of units, and it can be used, for example, when the batches (samples) are of different sizes.

Np chart for attributes

Select Np chart for attributes and click the OK button in the Startup Panel to begin this analysis. In these charts, we plot the number of defectives (per batch, per day, per machine) as in the C chart, but it is based on the binomial distribution.

P chart for attributes

Select P chart for attributes and click the OK button in the Startup Panel to begin this analysis. In these charts, we plot the percent of defectives (per batch, per day, per machine, etc.) as in the U chart. However, the control limits in this chart are based on the binomial distribution (of proportions).

Pareto chart analysis

Select Pareto chart analysis and click the OK button in the Startup Panel to begin this analysis. You can plot histograms by category, where the bars in the histogram are sorted in descending order. Such plots allow for the easy identification of the primary sources (categories) of quality problems.

See also, Common Types of Charts, Control Charts for Variables vs. Charts for Attributes, and the Quality Control Charts Index.