Z-Score in Table Matrix Visual

[tomperro]

I am trying to show the Z-Score for each employee in a table matrix.
I am using slicers to filter for different zones employees are in.

I am not sure how to write the DAX for the following variables:

TotalTests

TotalEmployees

AverageTests

StddDev 

With my slicer = "Zone 1"

Employee1 did 234 tests

Employee2 did 221 tests

Employee3 did 190 tests

Employee4 did 75 tests

Total Tests = 720

Total Employees = 4

TotalTests = 720

TotalEmployees = 4

AverageTests = 180

StddDev  = STDEVX.P (  ?  )  * should equal 72.39

ZScore = DIVIDE ( TotalTests - TotalEmployees , StddDev )

Desired Table Matrix:

Employee	TotalTests	AverageTests	Standard Deviation	Z-Score
Employee1	234	180	72.39	.75
Employee2	221	180	72.39	.57
Employee3	190	180	72.39	.14
Employee4	75	180	72.39	-1.45

[mh2587]

Did you try this one 

CountTests = Count(EmployeeData[Tests])

[mh2587]

//Replace table & Column with yours---This might help you
Z-Score = 
VAR TotalTests = SUM(EmployeeData[Tests])
VAR TotalEmployees = COUNTROWS(FILTER(EmployeeData, [Zone] = SELECTEDVALUE('Slicer'[Zone])))
VAR AverageTests = AVERAGE(EmployeeData[Tests])
VAR StddDev = STDEV.P(FILTER(EmployeeData, [Zone] = SELECTEDVALUE('Slicer'[Zone]))[Tests])
RETURN
    DIVIDE(TotalTests - TotalEmployees, StddDev)

[tomperro]

@mh2587 

Thank you for the quick response.

How do I get the count of tests?

Employee 1 did 234 tests. Each test is recorded as a new row in my tests table.

TestId	Employee
A13	Employee 1
B34	Employee 1
C43	Employee 1

[mh2587]

CountTests = Count(EmployeeData[Tests])

[tomperro]

@mh2587 

I have 2 tables with much more data than show below, just using these as examples.

Employee Data

Employee ID	Employee Name
1	Employee1
2	Employee2

Test Data

TestID	Employee ID
A13	Employee1
B34	Employee1
C43	Employee1
A13	Employee2
D56	Employee2
W43	Employee3

I need to show counts

Employee1 did 3 tests

Employee2 did 1 test

Employee3 did 1 test

[mh2587]

//Trythisone
Test Count = 
COUNTROWS(
    SUMMARIZE('Test Data', 'Test Data'[Employee ID], 'Test Data'[TestID])
)

[tomperro]

@mh2587 

Sorry for the back and forth, I wish there was a way to live chat.

That is giving me the count of test per employee, I need it to return the count of total tests.

Employee1 234 tests

Employee2 221 tests

Employee3 190 tests

Employee4 75 tests

I need the formula to return Total Tests = 720