calculate avg time - between multiple rows

Hi kymilue

It is quite tricky to cope with the concept of previous Row with pure DAX solutions.

I Suggest you use Power Query first !

From Power Query (Query Editor in Power Bi Desktop), 

1) Sort in ascending order by IDs (first) and by Scan Ts (second)

2) Create 2 custom columns with Power query: Index Column From 0 and Index Column from 1

3) Left join the table with itself by using Index and Index.1 as matching keys 1  // ID and ID as matching keys 2 (Remain Ctrl)

4) Develop and only keep the Scan.ts element

5) Create a new custom column in Power Query: ScanTs - Scan Ts.1

6) Format this new custom column as decimal and rename it TimeDifference

7) Close and Load the Query

8) Create the following measure: AvgTime = Average(YourTable[TimeDifference])

And enjoy :)

What this awesome video from MattAllington to see the different steps and understand this pattern: http://exceleratorbi.com.au/use-power-query-compare-database-records/