how to calculate schedule variance, effort variance, defect density in JIRA

[Nic Brough -Adaptavist-]

You probably need to find or write reports to do those for you.  Start with a clear definition of how you calculate them, and from what data in JIRA, that should help guide you as you look through the marketplace.

As an example, "defect density" probably implies something about testing cycles, so I'd be looking at the testing add-ons reporting.