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A quasi-experimental pre-test/post-test with control group design was employed to determine critical thinking gains in PLTL leaders and a control group comprising similar students who were unable for various reasons, but otherwise eligible, to serve as PLTL leaders. The PLTL training and leadership experience was the independent variable identifying the experimental group to determine if the dependent variable, critical thinking, improved as a result. To minimize validity threats of history, maturation, regression, and selection, a critical thinking post-test was given approximately 15 weeks after the pre-test to both the experimental and control groups.
This research study was approved by the Syracuse University Institutional Review Board. Prior to conducting the research, participants were provided with a written consent form explaining the details of the study, including both benefits and risks to participating. All participants indicated their consent to participate in the study by signing the consent form and returning it to a non-instructor/researcher third party. For privacy protection, each voluntary participant was assigned a unique 9-digit identification number by the third party administrator to use on all data collection instruments.
In keeping with the conventional PLTL model, undergraduate students who had obtained a final course grade of A or B in the second semester of introductory biology at a large, research university in the Northeastern United States were invited to participate in the study. Of the 75 interested participants, two groups were established: one group of students who were interested and able to complete the requirements of being a PLTL leader (experimental group) and one group of students who were interested but not able to be a leader due to various time/schedule constraints (control group). Interested participants who were 18 years of age or older completed a demographic survey to determine information regarding control variables for the data analyses of the study. Tables 1, 2, 3, and 4 provide the demographic make-up of the participants. While gender distribution of the two groups of participants was evenly matched, the PLTL group was comprised primarily of juniors while the non-PLTL group was comprised primarily of sophomores. About 60% of the participants were white/Caucasian, and approximately 40% were non-white including Hispanic/Latino, African American, Asian, and other racial groups. Racial/ethnic categories were those used by the university in this study. 80% of the participants were science majors. Over 60% of them had taken more than 6 science courses prior to the start of the academic term, and almost 75% of the participants took 2, 3, or 4 science courses during the academic term.
Table data removed from full text. Table identifier and caption: 10.1371/journal.pone.0115084.t001 Demographics for PLTL and Non-PLTL Groups (Class standing & Gender). Table data removed from full text. Table identifier and caption: 10.1371/journal.pone.0115084.t002 Demographics profile for PLTL and Non-PLTL Groups (Ethnicity). Racial categories used by the university in this study.
Table data removed from full text. Table identifier and caption: 10.1371/journal.pone.0115084.t003 Major and Number of Science Courses taken Prior to Spring 2011 for PLTL and Non-PLTL Groups. Table data removed from full text. Table identifier and caption: 10.1371/journal.pone.0115084.t004 Number of Science Courses taken During Spring 2011 for PLTL and Non-PLTL Groups. During the first week of classes, the valid and reliable California Critical Thinking Skills Test (CCTST) was administered to all participants in the experimental and control groups. At the end of the semester, the same test was administered as a posttest, along with an open-ended questionnaire targeting participants’ perceptions of critical thinking and how it changed throughout the semester.
The instructional intervention was composed of (a) peer leader training and (b) peer-led workshops throughout the semester. The potential impact of the PLTL training and leadership experience on critical thinking skills was dependent on leaders’ workshop practices. A two-credit course was offered that related educational research literature on students and learning to classroom applications in problem-solving activities. The peer leaders met with a learning specialist for one 55-minute class each week for 13 weeks to discuss teaching and learning theory and how to apply it conceptually, debrief on previous weeks’ sessions, and practice problem-solving strategies by collaboratively working on instructor-generated content problems [25]. During the first class, the learning specialist discussed the PLTL instructional model. Peer leaders were also provided with a PLTL leader handbook [45] that included many assigned readings on learning theory and group dynamics. At the start of each class succeeding the first, the learning specialist would either do a short activity related to the weekly reading assignment or ask if there were any questions about the assigned readings. Peer leaders were then able to debrief on the previous weeks’ sessions. During the debriefing time, peer leaders would share personal experiences with the other leaders, as well as the learning specialist. They would both offer and receive suggestions on how to handle various issues that arose during their PLTL workshops. Following the debriefing time, the learning specialist passed out a problem set for the week. Problem sets were developed based on the weekly content covered by the Biology instructor. Each problem set had several activities for the workshop students to engage in. The learning specialist modeled the problem-solving methods each week by having the peer leaders collaborate in small groups on the problem-solving activities much like their students should. While answers were generally not provided to the problem set activities, peer leaders were able to ask for clarification or helpful hints on any of the activities.
After the leader training class each week, the peer leaders facilitated a one-hour PLTL session for a group of students of their own (between one and ten, depending on how many students attended the workshop), without the presence of the instructor or learning specialist. Leaders offered guidance and support to their own students through the thought processes of solving the same problems they themselves worked on in their class with the learning specialist and other leaders. Peer leaders were required to keep a weekly written journal of their PLTL workshop experiences. Journal entries were submitted within three days of the workshop time. While journal entries varied among the leaders, peer leaders generally reflected on how their workshop went for the week. Reflections included how they thought the workshop went, what problems the students had, how the students interacted with each other and with them, etc. In addition to the journal entries, peer leaders were required to work with a partner and develop a problem set based on the teaching and learning strategies discussed throughout the PLTL leader training course. The problem set had to be a topic that had not been covered in a previous problem set or that their students had had difficulty with previously in the semester.
Statistical analyses of the quantitative data (S1 Dataset) associated with the CCTST were performed through a statistical software package, SPSS 19. Among the experimental group participants, a one-way repeated measures analysis of variance (RM ANOVA) was conducted to analyze overall critical thinking scores. Paired t-tests were also performed for each of the five sub-scale scores to examine differences in critical thinking skills as measured by the CCTST prior to the instructional intervention and immediately following the PLTL training and leadership experience. To increase statistical accuracy, gender, ethnicity, class standing, major and number of science courses taken prior to and during the Spring 2011 semester were analyzed as co-variables. Overall critical thinking scores were compared between the PLTL group and the non-PLTL group using mean, standard deviation, and two-way RM ANOVA. The two-way RM ANOVA was applied to the data because there were paired pre- and post-test scores, as well as a comparison group. Although the total pre- and post-test scores of the PLTL and control groups were normally distributed, there was a non-normal distribution of data in either the pre-test or the post-test of the five sub-scales of critical thinking. For this reason, nonparametric analyses of the five sub-scales were conducted. Qualitative data obtained through the open-ended critical thinking questionnaire was reviewed and analyzed by coding the responses of the participants as “perceived improvement in critical thinking skills” or “did not perceive improvement in critical thinking skills” to determine if participant self-report coincided with actual critical thinking test score data. Additional codes of participants’ responses were developed on the basis of emerging information and further analyzed to identify common themes about factors perceived to influence critical thinking skills.
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