Differnce Between Ragged and Skip level Hierarchy in OBIEE11g

 Ragged  Hierarchy:

         A hierarchy in which all the lowest-level members do not have the same depth.
 For example: a Time hierarchy might have data for the current month at the day level, the previous month's data at the month level, and the previous 5 years' data at the quarter level. This type of hierarchy is also known as an unbalanced hierarchy.

Skip-level  Hierarchy:

A hierarchy in which certain members do not have values for certain higher levels.
For example: in the United States, the city of Washington in the District of Columbia does not belong to a state. The expectation is that users can still navigate from the country level (United States) to Washington and below without the need for a state.