If you want blanks rather than NULL, then:
CASE WHEN ALTotalUnits / TotalProfiledHours >= 3 THEN CAST(ALTotalUnits AS varchar(30)) ELSE '' END AS [Higher than 3 Weeks],
CASE WHEN ALTotalUnits / TotalProfiledHours < 3 THEN '' ELSE CAST(ALTotalUnits AS varchar(30)) END AS [Lower than 3 Weeks]
SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".