G/T Chart (Time Between Events)

Monitor time intervals between rare events or failures using geometric distribution control charts.

Chart Overview & Applications

Control Limits & Statistical Foundation

Reading the G and T Rare-Event Chart

Example Chart & Pattern Recognition

sixsigmacenter.com Implementation Guide

Platform Features for G/T Charts

• • Geometric Distribution Analysis: Automatically handles rare event statistics
• • Flexible Input: Supports both count and time-based data
• • Probability-Based Limits: Control limits based on statistical theory
• • Trend Detection: Identifies improving or deteriorating patterns

Preparing Your Data for Upload

• • One row per rare event, in chronological order. G and T charts plot the gap between events, so the file records events — not periods with zero events.
• • For a G chart include a units-produced-since-last-event column; for a T chart include the event timestamp or the elapsed time since the previous event.
• • Do not delete the long quiet stretches. A large gap is the improvement signal these charts exist to detect.
• • Keep one failure mode per file. Mixing infection types or defect modes destroys the constant-rate assumption behind the limits.

Aim for at least 20 to 25 events before setting baseline limits. Below that the estimated rate is too unstable to trust an out-of-control signal.

Example Data Layout for G/T Chart

Event tracking with units inspected and time elapsed between events. Lower values indicate deteriorating performance requiring investigation. Sample Size Recommendation: Minimum 10-15 events for reliable control limits - requires sufficient event history for stable geometric distribution parameters.

This is how your spreadsheet or CSV file should be structured before you upload it. Match the column names, keep one row per observation, and leave the analysis to the platform.