Synthetic data · generated in your browser
Quarterly statistical report (demo)
Y3 Q4 · synthetic incidents per 1,000 attendances
- Incidents
- 93
- Attendances
- 44,761
- Rate per 1,000
- 2.08
- 95% interval
- 1.68–2.55
Findings
- In Y3 Q4 there were 93 incidents across 44,761 attendances, a rate of 2.08 per 1,000 (95% interval 1.68 to 2.55).
- The rate sits inside the control limits, so on the chart this is an ordinary quarter.
- Against the previous quarter (Y3 Q3, 1.98 per 1,000), the rate ratio is 1.05 (95% interval 0.78 to 1.41). The interval includes 1, so the data do not support calling this a change.
- Against the same quarter a year earlier (Y2 Q4, 1.83 per 1,000), the rate ratio is 1.14 (95% interval 0.83 to 1.56). The interval includes 1, so the data do not support calling this a change.
- Across all twelve quarters, Y3 Q2 sat outside the control limits.
You planted a +50% change in Y3 Q2. The chart caught it.
Method
Rates are incidents per 1,000 attendances. Intervals are exact Poisson (Garwood) intervals. The u-chart centre line is the pooled rate across all twelve quarters, and each quarter's limits sit three standard errors either side of it, where a standard error is √(ū / n) for n thousand attendances. Rate ratios use the exact conditional binomial interval. All data are synthetic.