I am trying to measure the cycle time of my team. The problem is that the issues (tasks or stories) have very different sizes. Sometimes someone just creates a task like: "Create a backend api", that doesn't deliver value for the final customer and is very small. And sometimes the Product Owner creates tasks like "Implement anti fraud system" which are very large.
How should we measure the cycle time? One convention that we have been using is to only measure stories' cycle time, not tasks' nor subtasks'.
How should this be done?