Comparing and contrasting different algorithms leads to increased student learning

Comparing and contrasting different solution approaches is known in math education and cognitive science to increase student learning -- what about CS? In this experiment, we replicated work from Rittle-Johnson and Star, using a pretest--intervention--posttest--follow-up design (n=241). Our intervention was an in-class workbook in CS2. A randomized half of students received questions in a compare-and-contrast style, seeing different code for different algorithms in parallel. The other half saw the same code questions sequentially, and evaluated them one at a time. Students in the former group performed better with regard to procedural knowledge (code reading & writing), and flexibility (generating, recognizing & evaluating multiple ways to solve a problem). The two groups performed equally on conceptual knowledge. Our results agree with those of Rittle-Johnson and Star, indicating that the existing work in this area generalizes to CS education.