Inconsistent application of mean and median for DORA metrics

Problem

• Deployment frequency is represented as a median
• Other CI/CD metrics are mean
• There is no way to control which calculation logic is used, which we would find beneficial.
• There is no explanation why one is used over the other for different metrics.

Proposal

• Simple: Provide better documentation on why each metric uses median or mean.
• Harder: Provide the ability to control which operation to use for each metric.