mdx - MDX の IIF 関数の間違った結果

Question

以下のようにクエリを書きました。

WITH 
  SET [kpi_study] AS 
    {[study].[study].[BHC June12]} 
  SET [geographic] AS 
    {[territory.market_hierarchy].[state].[HP]} 
  SET [brand] AS 
    {[brand.brand_hierarchy].[brand].[Gold Flake (Unspecified)]} 
  SET [edu12] AS 
    IIF
    (
      'All' = 'All'
     ,[education].[education].MEMBERS
     ,[education].[education].[All]
    ) 
SELECT 
  NON EMPTY 
    {[Measures].[tom]} ON COLUMNS
FROM [funnel_analysis]
WHERE 
  {[kpi_study]*[geographic]*[brand]};

結果:トム:4.19

Allの代わりに( SSC/HSC ) 他の値を渡す場合、常に同じ値を取得します。