Having the students reflect on sources of error encouraged questioning aspects of the experiment that they might have otherwise considered infallible, increasing awareness and motivating them to reduce those sources of error in their real lab work. Students were given formal instruction in error analysis. They learned to identify possible sources of error in four different categories: human, environmental, instrumental, and random error; statistical procedures of proficiency testing; error propagation and chi-squared analysis; and the confidence level/level of significance.