My name is Adam Z. I am a developer, and I started Story Estimate as a side project.
How is "Disagreement" indicator determined?
I use a coefficient of variation to determine the disagreement level among players.
Can I change my default estimation settings, so I don't have to change it every time?
Yes, if you have a permanent account. Go to your Settings and click on "Default Estimation Settings". We'll fill the new estimation page with your defaults when you start a new estimation. However, you can still change it.
Is it free?
All of the features are free, but some might become available only to paid accounts in the future... although unlikely. Just don't want to overpromise that this will be forever free.