Weibull Probability Plots with Batch Problems
When plotted points show an unexpected concentration of failures, a batch problem is likely to have been caused by changes made to:
• Production or assembly processes.
• Maintenance or overhaul schedules.
• Increases in service usage.
Other indications that a batch problem exists are the presence of many late suspensions and the closeness of serial numbers of failed parts. The Weibull probability plot is likely to show a steep slope followed by a shallow slope (which may be followed by another steep slope if the period of time being analysed is long enough).