Random Sample

Thanks for the response. I think I have solved with some Dax which creates a table for each column I want to randomise and forms a union of those tables. Its a long process but I think it will work. I just create a table per column for the sample spread? 

Random Selection with category filter and sample size =

VAR SampleSize = XX

VAR Cat_Name1TableWithRand =

TOPN (SampleSize, ADDCOLUMNS ( FILTER('Table_Name', 'Table_Name'[Column1] = "Cat_Name1"), "Rand", RAND () ), [Rand])

VAR Cat_Name2TableWithRand =

TOPN (SampleSize, ADDCOLUMNS ( FILTER('Table_Name', 'Table_Name'[Column1] = "Cat_Name2"), "Rand", RAND () ), [Rand])

VAR Cat_Name3TableWithRand =

TOPN (SampleSize, ADDCOLUMNS ( FILTER('Table_Name', 'Table_Name'[Column1] = "Cat_Name3"), "Rand", RAND () ), [Rand])

VAR UnionTable =

UNION (Cat_Name1TableWithRand , Cat_Name2TableWithRand , Cat_Name3TableWithRand )

RETURN UnionTable

If there is a quicker way, then great!