Table 2
Quantitative Variables.
| VARIABLE | DESCRIPTION AND CODING |
|---|---|
| Dependent Variable | |
| Student Course Grade | 1 = A, 0 = Any grade other than an A |
| Independent Variables | |
| OER | 1 = OER or no cost textbook, 2 = commercial textbook |
| First Generation | First Generation = 1, Continuing Generation = 0 |
| Pell Eligibility | Pell Eligible = 1, Not Pell Eligible = 0 |
| Race Other than White Only | 1 = Student identifies as a racial category other than white only; 0 = student identifies as white only |
| Class Standing | Class standing by credit hours. 3 = Senior, 2 = Junior, 1 = Sophomore, 0 = First Year. The reference group is first year students. |
| Disciplinary Group | Disciplinary group for each course. 0 = Humanities, 1 = Social Sciences, 2 = STEM. The reference group is humanities courses. |
| Overall Grade Point Average | Grade point average on a 4.0 scale |
Table 3
Descriptive Statistics.
| VARIABLES | FREQUENCY | |||
|---|---|---|---|---|
| Dependent variable | ||||
| Course Grade = A | 5,229 | |||
| Course Grade = Other than A | 4,201 | |||
| Categorical independent variables | ||||
| OER | 4,568 | |||
| Not OER | 4,862 | |||
| First Generation | 2,012 | |||
| Continuing Generation | 7,418 | |||
| Pell Eligible | 1,924 | |||
| Not Pell Eligible | 7,506 | |||
| Race = Not White Only | 4,376 | |||
| Race = White | 5,054 | |||
| Class Level: Freshman | 1,993 | |||
| Class Level: Sophomore | 2,945 | |||
| Class Level: Junior | 2,201 | |||
| Class Level: Senior | 2,291 | |||
| Disciplinary Group: STEM | 1,707 | |||
| Disciplinary Group: Social Sciences | 2,589 | |||
| Disciplinary Group: Humanities | 5,134 | |||
| Continuous Independent Variable | Mean | Standard Deviation | Min | Max |
| Student Grade Point Average | 3.238 | .598 | 0 | 4 |
Table 4
Logit Coefficients, Standard Errors and Odds Ratios (Overall Population).
| B | SE | OR | |
|---|---|---|---|
| Constant | –9.722*** | .232 | .00006 |
| OER | .491*** | .052 | 1.634 |
| First-Generation | –.117 | .069 | .890 |
| Pell Eligibility | –.067 | .070 | .935 |
| Race = Not White Only | .177** | .053 | 1.193 |
| Class level (Reference Group: First-Year Students) | |||
| Sophomores | .170* | .073 | 1.186 |
| Juniors | .326*** | .078 | 1.385 |
| Seniors | .417*** | .080 | 1.517 |
| Disciplinary Group (Reference Group: Humanities) | |||
| Social Sciences | .092 | .062 | 1.097 |
| STEM | –.961*** | .073 | .383 |
| Overall GPA | 2.657*** | .061 | 14.250 |
| Observations | 9,430 | ||
| LR R2 | .2671 | ||
| Log Likelihood | –4749.4911 | ||
| df_m | 10 | ||
| LR χ2 | 3461.48 | ||
[i] b = unstandardized regression coefficient; OR = odds ratio; ***p < .001, **p < .01, *p < .05.
Table 5
Logit Coefficients, Standard Errors and Odds Ratios (First-Generation Students).
| B | SE | OR | |
|---|---|---|---|
| Constant | –7.733*** | .419 | .0004 |
| OER | .567*** | .108 | 1.763 |
| Pell Eligibility | –.161 | .111 | .852 |
| Race = Not White Only | .285* | .121 | 1.330 |
| Class level (Reference Group: First-Year Students) | |||
| Sophomores | .160 | .152 | 1.173 |
| Juniors | .445** | .162 | 1.561 |
| Seniors | .483** | .168 | 1.622 |
| Disciplinary Group (Reference Group: Humanities) | |||
| Social Sciences | –.015 | .130 | .985 |
| STEM | –1.22*** | .165 | .295 |
| Overall GPA | 2.283*** | .119 | 9.802 |
| Observations | 2,012 | ||
| LR R2 | .2341 | ||
| Log Likelihood | –1061.7867 | ||
| df_m | 9 | ||
| LR χ2 | 649.17 | ||
[i] b = unstandardized regression coefficient; OR = odds ratio; ***p < .001, **p < .01, *p < .05.