Average Days to Complete a Task

Hi, shansenTrek 

Based on your description, I created data to reproduce your scenario.

Table:

You may create two measures as below.

SumDays = 
var t1 = 
SUMMARIZE(
    'Table',
    'Table'[Project Name],
    'Table'[Task Names],
    "Start Date",FIRSTDATE('Table'[Date]),
    "Last Date",LASTDATE('Table'[Date])
)
var t2 = 
ADDCOLUMNS(
    t1,
    "# of Days",DATEDIFF([Start Date],[Last Date],DAY)
)
var _task = SELECTEDVALUE('Table'[Task Names])
return
SUMX(
        FILTER(
            t2,
            [Task Names] = _task
        ),
        [# of Days]
)

AvgDays = 
var t1 = 
SUMMARIZE(
    'Table',
    'Table'[Project Name],
    'Table'[Task Names],
    "Start Date",FIRSTDATE('Table'[Date]),
    "Last Date",LASTDATE('Table'[Date])
)
var t2 = 
ADDCOLUMNS(
    t1,
    "# of Days",DATEDIFF([Start Date],[Last Date],DAY)
)
var _task = SELECTEDVALUE('Table'[Task Names])
return
DIVIDE(
    SUMX(
        FILTER(
            t2,
            [Task Names] = _task
        ),
        [# of Days]
    ),
    COUNTROWS(
        FILTER(
            t2,
            [Task Names] = _task
        )
    )
)

Result:

Best Regards

Allan

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