This what?
This allows you to point to people and things.
- You can use this with a noun ("This method")
OR - You can use this by itself--as a pronoun ("This worked well for group A")
This as a pronoun
If you use this by itself (as a pronoun) in a more complex text, the reader can quickly get confused–they won't be able to easily see what you are pointing at.
Choosing to use this with a noun (this analysis) rather than by itself (this) allows you to point back to one specific part of the previous text.