Assessment and Discussion
The CDF was initially piloted in a section of Principles of Ecology
in early fall 2013 and revised based on informal student feedback.
Then, with IRB approval (IRB 2014-00171), during fall 2013 and
spring 2014, we compared three experimental sections (CDF
exercise) and two control sections (paper-and-pencil-based version) of Environmental Science and of Ecology (both non-majors
courses). In all sections, we gave a pre- and post-survey to assess
student preparedness and understanding; students answered
using a 5-point Likert scale (Table 2). We analyzed the numerical
results of the surveys using Microsoft Excel, R, and Mathematica.
The post-survey included four free-response questions. We identified the topics students commented on in their responses (e.g.,
math, interactivity, etc.) and counted the number of students
whose comments included each topic in each question.
Both groups responded more favorably in the post-survey as
compared to the pre-survey. For example, for the control section,
a Wilcoxon signed-rank test indicated that the students reported
more confidence in their ability to compute Simpson’s Diversity
Index on the post-survey than on the pre-survey (V = 148,
p < .001). On the same question, the experimental group also
reported more confidence on the post-survey compared to the pre-survey (V = 147.5, p < .001). A Mann-Whitney test found no statistically significant difference in the post-test responses between the
groups (U = 251, p = .062) (Figure 6). These numerical results suggest both that the CDF exercise is effective in promoting student
learning and that the use of technology did not become a distraction
or otherwise detract from students’ learning.
The interactive CDF lab was just as effective in promoting
learning, but also, based on instructors’ observations and responses
to the open-ended survey questions, increased student engagement.
Students enjoyed interactive graphs and having the software check
their work, with one-sixth of the students who completed the CDF
lab commenting that the interactivity was their favorite aspect. In
fact, interactivity was the most frequently mentioned aspect of the
lab mentioned in Question 9 (Table 2). Student comments
included, “My favorite part was that the program explained everything very well and you could move the graphs,” and “I liked the
graphs and stuff it displayed to help us understand.”
Not all students seemed as comfortable with computer-based
labs as we had expected, although only one student specifically mentioned the computer as a least favorite aspect, and two included it as
a positive. There was some evidence in the open-ended questions to
suggest that the CDF format made the lab easier to follow. While two
students from each group (paper-based [control] and CDF) commented in Question 10 that the instructions were confusing to them,
two other students who completed the CDF version commented in
Question 9 that the clarity of instructions was one of their favorite
features, compared to none in the control group.
Even with the interactive exercise, we had comments like “I disliked the large equation,” although math was mentioned as the least
favorite aspect of the activity by only about a quarter of the students in the experimental section compared to half for the students
with the paper version of the lab. Interestingly, the most dramatic
pattern in the open-ended responses was that well over two-thirds
of the students in the control group commented about mathematics
Figure 5. For Question 5, students can move the sliders to change the numbers of individuals of each species and see the effect
on the rank abundance curve and Simpson’s Diversity index.