Let's say I want to ask a user wether she likes a song or not.
If I ask her to answer:
- Don't know this song
I guess there's a risk that she will choose the last option for songs she knows only a bit.
However, if I use grade scale and ask her to answer with one of the following options:
- Definitely yes!
- Maybe yes
- Rather no
- Definitely not!
- Don't know
I guess there will be fewer "Don't know" answers, because if a user knows the song only a bit, she will have a chance to "hedge" her answer and answer with maybe/rather answers.
Is there any research supporting my guess?