Help for simple measure

Hello Community,

I am struggeling by creating a measure and asking for help.

A product_table that holds all information and is distinct:

And a test sample_table where multiple tests have ben created by each product:

In the samples table multiple tests have been perfomed and they are all in the column Test

The relationship is 1 to n from product_table to sample_table - filtering both directions.

I now would like to analyze the samples by creating slicers in the sample table for the performed tests like "Strength Test" and have the average Height for all products in that test line.

Sliced result in samples_table:

How can I now calculate the average height of all sliced products? 

I tried to count the rows on the sliced sample_table like that:

Count of Values = CALCULATE(DISTINCTCOUNT(samples_table[Product]))

and then perform the 

Average = DIVIDE(SUM(product_table[Height]),[Count of Values])

 but that gives me the wrong results.

Your help is much appreciated.