As you can probably imagine, when you are faced with a large project that is attempting a complex subject matter or high-risk context, you will need to consider complexity and risk when planning the business analysis approach, as well as the specific activities. 

For example, if you are planning the business analysis work activities for an airline flight control system, there will be a lot of very detailed and accurate analysis required upfront and potentially on an ongoing basis, too. However, if you were planning business analysis activities for a mobile application development project that is focused on customer experience, you will probably be more interested in planning with an adaptive approach in mind.

Other factors that can affect the complexity of the business analysis effort could include geography and cultural considerations, technology complexities, the number of systems involved, and the sheer size of the change. A change affecting everyone in an organization is likely to be more complex than if only a small isolated team in an organization is affected.