Hi,
I am a relatively new Scrum Master and I am dealing with sizing stories with a team of programmers which are Juniors.
At certain user stories the programmers are not able to size the case, since they do not know which technical solution they could apply, they tell me they would have to investigate on it. So have begun to use spikes stories. I do not size them, but they are assigned on them on currenty sprint so that they can use some time to investagate on a user story for next sprint so we size it.