Smallest Deposit Group per Magic Wand Size

SELECT DepositGroup
 FROM WizzardDeposits
 GROUP BY DepositGroup
 HAVING AVG(MagicWandSize) IN (SELECT MIN(DepositGroupsWithAverageWandSizes.[Average magic wand size]) AS [Min average wand size]
                               FROM (SELECT DepositGroup,
                                            AVG(MagicWandSize) AS [Average magic wand size]
                                      FROM WizzardDeposits
                                      GROUP BY DepositGroup) AS DepositGroupsWithAverageWandSizes)