Do undergraduates actually learn anything from a TIEE laboratory?

I assessed the effectiveness of an inquiry-based/active-learning laboratory on student learning for the second year.  Students used a TIEE (Teaching Issues and Experiments in Ecology) experiment on soil invertebrate diversity in a general ecology laboratory to develop a hypothesis and test it.  Student learning was assessed by a previously developed and refined pre-test/post-test instrument.  Eight students (out of 22) in the laboratory section took both the pretest and the post-test.  Students were evenly distributed among sophomores, juniors, and seniors.  Most students had previous experience developing testable hypotheses and writing research papers, but most had no experience writing research proposals or conducting research.  Virtually all students agreed or strongly agreed that they could analyze and describe an experimental design, both before and after the lab.  There was less confidence for writing testable hypotheses and designing an experiment; while there was very little difference between the pre- and the post-test for the former area, student assessment of their ability to design an experiment increased.  All students were able to correctly identify a null hypothesis and most were able to assign a correct P-value, but there was confusion regarding whether to accept or reject the null hypothesis.  Student understanding of content was higher for some areas in the post-test, although other areas showed little change.  While student interpretation and explanation of results in the post-test improved, mastery of the writing skills needed for a scientific report remained mixed.  Students did learn from this laboratory.  However, there were gaps between student self-assessment and instructor assessment, showing areas that need to be emphasized in the future.  This includes better statistical instruction and scientific writing.  As similar results were obtained from the previous year's class, this suggests that further changes need to be made both in the course and in the department's curriculum.