1. I took a shower so I cleaned the room.
2. I took a shower, so I cleaned the room.
3. I took a shower so that I cleaned the room.
(What does #1 mean? Does it mean #2 or #3?)
4. I took a raincoat so I might wear it when it rained.
5. I took a raincoat, so I might wear it when it rained.
6. I took a raincoat so that I might wear it when it rained.
(Does #4 mean #5 or #6?)
1 and 2 mean the same; 3 does not.
4, 5, and 6 all mean the same.