The Interaction of OER Use and Course Difficulty on Student Course Grades in a Community College
with students ’ course grades vary with course difficulty ?
Prior academic performance is particularly important to control for because it is such a strong predictor of performance on learning assessments (
Cassidy , 2015 ).
Method
The study was conducted in a community college in Virginia that has adopted an OER-based pedagogy that allows students to earn associate degrees with zero dollars spent on textbooks ( DeMarte & Williams , 2015 ; Wiley , Williams , DeMarte , & Hilton , 2016 ). Data were obtained from 35 courses , which had both non-OER and OER sections , offered during the summer and fall semesters of 2016 . Those courses were taught by 388 instructors . Some of the instructors taught courses or sections in the ZTC degree with OER and also taught courses outside of the ZTC degree with traditional textbooks . The courses included a wide range of subjects including business , mathematics , computer programming , biology , chemistry , history , music , and sports , which was a representative list of courses offered in a community college . Approximately 25,117 course grades were included but with listwise deletion of data based on the eventual covariates considered , 15,633 course grades were considered . Data were extracted from the college ’ s archives .
The dependent variable , Course Grades , estimated students ’ learning outcomes and were reported on a fivepoint scale , A , B , C , D , and F ( 4,3,2,1,0 ). Five independent variables were included in the study : OER Course ( Yes / No ), Gender ( Male / Female ), Pell Eligibility ( Yes / No ), Course Difficulty ( continuous ) and Previous GPA ( continuous ).
OER Course was measured as a binary variable with 1 being OER course and 0 being non-OER course . Self-reported gender in the system was binary , male and female . Pell eligibility ( 1 : eligible ; 0 : not eligible ) and prior GPA were extracted for each student from the college ’ s records . Prior GPA was standardized to a z-score , which has a mean of 0 and standard deviation ( SD ) of 1 ( original mean = 2.94 ; SD = 0.78 ). The course difficulty variable was based on failure rates in the current courses . It was created by calculating the proportion of students achieving a D grade or lower across all sections of each course ( e . g ., if 80 % of students who took the course received a D or lower grades , the difficulty would be 0.8 ). Course difficulty was then standardized ( i . e ., standardized difficulty = ( raw difficulty – mean difficulty of all courses ) / SD of all courses ) around the mean failure rate of 0.28 ( SD = 0.8 ; Range , 0.08 to 0.43 ) to render a continuous variable with mean of 0 and SD of 1 . Hence , the larger the difficulty score , the more difficult the course was , and positive course difficulty scores ( i . e ., above mean ) meant that the course was more difficult than the courses with negative difficulty scores ( i . e ., below mean ).
The purpose of standardizing the two continuous variables ( prior GPA and course difficulty ) was for inter-
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