Do programmer pairs make different mistakes than solo programmers?

Objective: Comparison of program defects caused by programmer pairs and solo developers.Design: Analysis of programs developed during two counter balanced experiments.Setting: Programming lab at University.Experimental units: 42 programs developed by computer science students participating in an extreme programming lab course.Main outcome measures: Programmer pairs make as many algorithmic mistakes but fewer expression mistakes than solo programmers.Results: The second result is significant on the 5% level.Conclusions: For simple problems, pair programming seems to lead to fewer mistakes than solo programming.