  Background: Proof Blocks is a software tool that enables students to
construct proofs by assembling prewritten lines and gives them automated
feedback. Prior work on learning gains from Proof Blocks has focused on
comparing learning gains from Proof Blocks against other learning activities
such as writing proofs or reading.
  Purpose: The study described in this paper aims to compare learning gains
from different variations of Proof Blocks. Specifically, we attempt to quantify
the difference in learning gains for students who complete Proof Blocks
problems with and without distractors.
  Methods: We conducted a randomized controlled trial with three experimental
groups: a control group that completed an off-topic Proof Blocks activity, one
that completed a \tool{} activity without distractors, and one that completed a
Proof Blocks activity with distractors. All three groups read a book chapter on
proof by induction before completing their activity.
  Findings: The group that completed the Proof Blocks activity with distractors
performed better on the posttest than the group that completed the Proof Blocks
without distractors, who in turn performed better than the group that completed
the off-topic Proof Blocks activity. However, none of these differences were
statistically significant. While the results of this study are inconclusive, we
hope that it can serve as a foundation for future work.
