Average of the difference between modified dates with different filters

[MichalSa]

Hi 

I'm trying to calculate the average of the difference between modified dates with different filters.

The field is called 'Modified date' and is changed when there is a status change

I'm trying to calculate the avg difference of the modified date field when:

1. the status field is equal to "Closed" 

2. the status field is equal to "New" 

Trying to use the below calculation without success:

= avg (({<[Status] = {'Closed'}>} [Modified Date] ) -  {<[Status] = {'New'}>} [Modified Date])

Thanks for your help!