Table 1
Number of observations.
| FACULTY | PROGRAMS | COURSES | COURSE SECTIONS |
|---|---|---|---|
| Arts | 36 | 701 | 5725 |
| Business | 20 | 250 | 5516 |
| Design | 8 | 130 | 475 |
| Health | 8 | 95 | 475 |
| Science & Horticulture | 15 | 190 | 1414 |
| Total | 87 | 1366 | 13605 |
[i] Note. One program was cross listed in two Faculties.
Table 2
Definitions of Key Variables Categorized by Their Roles in the Statistical Model.
| VARIABLE TYPE | DEFINITION |
|---|---|
| Predictor | |
| ZTC Status | Indicates whether a given course session was designated as zero-textbook cost offering. |
| Outcomes | |
| GPA | The estimated average GPA for a given course section. |
| Withdrawal Rates | The proportion of students who withdrew from a given course section. |
| Seats Fill Rates | The proportion of available seats that were occupied by students in a given course section. |
Table 3
Distributions of ZTC Offering by Course Level or Discipline.
| COURSE LEVEL | PERCENT | BY DISCIPLINE | PERCENT |
|---|---|---|---|
| Year 1 | 59.27% | Arts | 62.55% |
| Year 2 | 14.27% | Business | 17.79% |
| Year 3 | 15.54% | Design | 7.71% |
| Year 4 | 8.98% | Science & Horticulture | 6.05% |
| Year 5 | 1.50% | Health | 5.89% |
| Year 6 | 0.43% |
Figure 1
Specification of Nested Data Structure for Multilevel Modelling.
Note: This figure illustrates how the nested structure was set up for our analyses using multilevel modeling. Course sections offered over the years were specified to be nested within each course.
Table 4
Outcomes by ZTC status (unclustered and clustered means).
| OUTCOMES | UNCLUSTERED MEANS | CLUSTERED MEANS | ||||
|---|---|---|---|---|---|---|
| NON-ZTC | ZTC | DIFFERENCE | NON-ZTC | ZTC | DIFFERENCE | |
| GPA | 2.64 | 2.91 | 0.27 | 3.02 | 3.07 | 0.05 |
| Seats Fill Rates | 78.40% | 77.70% | –0.70% | 69.00% | 68.90% | –0.10% |
| Withdrawal Rates | 8.00% | 6.70% | –1.30% | 6.10% | 6.10% | 0.00% |
| AB Rates | 24.50% | 22.90% | –1.60% | 76.20% | 77.80% | 1.60% |
| DFW Rates | 17.80% | 15.50% | –2.30% | 12.10% | 11.60% | –0.50% |
[i] Note. The difference is calculated by subtracting the values for the non-ZTC condition from those for the ZTC condition. Analyses of AB and DFW rates were not included in the main manuscript. Please refer to Appendix B for the definitions of these variables, the results of their analyses, and an explanation for their exclusion.
Table 1
Multilevel Regression Output for Outcome: GPA (Possible Range 0–4.33).
| PARAMETERS | ESTIMATE | SE | STATISTIC | DF | 95% CI |
|---|---|---|---|---|---|
| Intercept | 2.68a | 0.03 | 80.73 | 1341.60 | (2.61, 2.74) |
| ZTC Status = 1 | 0.04 | 0.02 | 2.20 | 327.87 | (0.00, 0.08) |
| Academic Year 19/20 | 0.14a | 0.01 | 10.65 | 12136.67 | (0.12, 0.17) |
| Academic Year 20/21 | 0.12a | 0.01 | 9.32 | 12113.85 | (0.09, 0.14) |
| Academic Year 21/22 | –0.00 | 0.01 | –0.10 | 12220.81 | (–.03, 0.03) |
| Spring Semester | 0.04a | 0.01 | 3.51 | 12829.37 | (0.02, 0.06) |
| Summer Semester | 0.12a | 0.01 | 8.92 | 12581.28 | (0.09, 0.10) |
| School of Business | –0.17a | 0.04 | –4.13 | 1165.45 | (–.24, –0.09) |
| School of Design | 0.36a | 0.05 | 6.97 | 1465.11 | (0.26, 0,46) |
| Faculty of Health | 1.03 | 0.06 | 17.11 | 1448.94 | (0.91, 1.14) |
| Faculty of Science & Horticulture | –0.13b | 0.04 | –2.86 | 1373.39 | (–.21, –0.04) |
| Course Level 2 | 0.11 | 0.04 | 2.67 | 1240.33 | (0.03, 0.18) |
| Course Level 3 | 0.26a | 0.04 | 6.54 | 1313.13 | (0.18, 0.33) |
| Course Level 4 | 0.45a | 0.05 | 10.01 | 1329.06 | (0.37, 0.54) |
| Course Level 5 | 0.46a | 0.08 | 5.81 | 1119.70 | (0.31, 0.62) |
| Course Level 6 | 0.69a | 0.12 | 5.71 | 1141.37 | (0.45,0.93) |
| sd Intercept | 0.44 | ||||
| cor Intercept & ZTC Status | 0.05 | ||||
| sd ZTC Status | 0.15 | ||||
| sd Residual | 0.52 |
[i] Note: SE = standard error; df = degrees of freedom; 95%CI = lower and upper confidence limits for 95% confidence intervals; aEstimates are statistically significant at p < .001; bEstimates are statistically significant at p < .01.
Table 2
Multilevel Regression Output for Outcome: Seats Fill Rate (Possible Range 0–1).
| PARAMETERS | ESTIMATE | SE | STATISTIC | DF | 95% CI |
|---|---|---|---|---|---|
| Intercept | 0.79a | 0.01 | 57.17 | 1262.21 | (0.76, 0.81) |
| ZTC Status = 1 | 0.01 | 0.01 | 0.87 | 177.95 | (–0.01, 0.02) |
| Academic Year 19/20 | –0.02a | 0.00 | –3.86 | 12425.42 | (–0.02, –0.01) |
| Academic Year 20/21 | –0.03a | 0.00 | –6.74 | 12409.89 | (–0.03, –0.02) |
| Academic Year 21/22 | –0.06a | 0.00 | –15.03 | 12448.50 | (–0.07, –0.05) |
| Spring Semester | –0.02a | 0.00 | –4.35 | 12993.51 | (–0.02, –0.01) |
| Summer Semester | 0.04a | 0.00 | 8.57 | 12751.65 | (0.03, 0.04) |
| School of Business | 0.03 | 0.02 | 1.45 | 1162.79 | (–0.01, 0.06) |
| School of Design | 0.07a | 0.02 | 3.24 | 1300.22 | (0.03, 0.11) |
| Faculty of Health | 0.01 | 0.02 | 0.28 | 1327.32 | (–0.04, 0.06) |
| Faculty of Science & Horticulture | –0.16a | 0.02 | –8.98 | 1270.30 | (–0.20, –0.13) |
| Course Level 2 | –0.10a | 0.02 | –5.79 | 1200.75 | (–0.13, –0.06) |
| Course Level 3 | –0.06a | 0.02 | –3.90 | 1245.93 | (–0.10, –0.03) |
| Course Level 4 | –0.12a | 0.02 | –6.24 | 1254.65 | (–0.16, –0.08) |
| Course Level 5 | –0.15a | 0.03 | –4.23 | 1127.62 | (–0.21, –0.08) |
| Course Level 6 | –0.20a | 0.05 | –3.81 | 1145.47 | (–0.30, –0.01) |
| sd Intercept | 0.20 | ||||
| cor Intercept & ZTC Status | 0.11 | ||||
| sd ZTC Status | 0.05 | ||||
| sd Residual | 0.16 |
[i] Note: SE = standard error; df = degrees of freedom; 95%CI = lower and upper confidence limits for 95% confidence intervals; aEstimates are statistically significant at p < .001; bEstimates are statistically significant at p < .01.
Table 3
Multilevel Regression Output for Outcome: Withdrawal Rate (Possible Range 0–1).
| PARAMETERS | ESTIMATE | SE | STATISTIC | DF | 95% CI |
|---|---|---|---|---|---|
| Intercept | 0.07a | 0.00 | 18.31 | 1339.31 | (0.06, 0.07) |
| ZTC Status = 1 | –0.00 | 0.00 | –1.71 | 313.45 | (–0.01, 0.00) |
| Academic Year 19/20 | 0.02a | 0.00 | 8.44 | 12664.61 | (0.01, 0.02) |
| Academic Year 20/21 | 0.02a | 0.00 | 12.24 | 12669.19 | (0.02, 0.03) |
| Academic Year 21/22 | 0.03a | 0.00 | 13.18 | 12759.523 | (0.02, 0.03) |
| Spring Semester | 0.01a | 0.00 | 5.23 | 13403.79 | (0.01, 0.01) |
| Summer Semester | –0.01b | 0.00 | –2.43 | 13223.56 | (–0.01, –0.00) |
| School of Business | –0.01 | 0.00 | –1.88 | 1024.67 | (–0.02, 0.00) |
| School of Design | –0.06a | 0.01 | –9.87 | 1676.36 | (–0.07, –0.05) |
| Faculty of Health | –0.06 | 0.01 | –9.14 | 1499.50 | (–0.07, –.05) |
| Faculty of Science & Horticulture | 0.02a | 0.01 | 3.20 | 1357.39 | (0.01, 0.03) |
| Course Level 2 | –0.01b | 0.00 | –2.53 | 1174.21 | (–0.02, –0.00) |
| Course Level 3 | –0.01a | 0.00 | –3.34 | 1265.14 | (–0.02, –0.01) |
| Course Level 4 | –0.03a | 0.01 | –5.79 | 1315.89 | (–0.04, –0.02) |
| Course Level 5 | –0.06a | 0.01 | –6.57 | 1022.11 | (–0.07, –0.04) |
| Course Level 6 | –0.08a | 0.01 | –5.92 | 1069.89 | (–0.10, –0.05) |
| sd Intercept | 0.04 | ||||
| cor Intercept & ZTC Status | 0.26 | ||||
| sd ZTC Status | 0.01 | ||||
| sd Residual | 0.08 |
[i] Note: SE = standard error; df = degrees of freedom; 95%CI = lower and upper confidence limits for 95% confidence intervals; aEstimates are statistically significant at p < .001; bEstimates are statistically significant at p < .01.
Table 4
Multilevel Regression Output for Outcome: AB Rate (Possible Range 0–1).
| PARAMETERS | ESTIMATE | SE | STATISTIC | DF | 95% CI |
|---|---|---|---|---|---|
| Intercept | 0.64a | 0.01 | 64.38 | 1369.32 | (0.62, 0.66) |
| ZTC Status = 1 | 0.01 | 0.01 | 1.35 | 328.57 | (–.00, 0.02) |
| Academic Year 19/20 | 0.05a | 0.00 | 12.00 | 12341.53 | (0.04, 0.06) |
| Academic Year 20/21 | 0.04a | 0.00 | 9.54 | 12332.88 | (0.03, 0.05) |
| Academic Year 21/22 | 0.00 | 0.00 | 0.31 | 12445.52 | (–0.01, 0.01) |
| Spring Semester | 0.02a | 0.00 | 4.23 | 13056.75 | (0.01, 0.02) |
| Summer Semester | 0.03a | 0.00 | 7.42 | 12835.57 | (0.02, 0.04) |
| School of Business | –0.05a | 0.01 | –4.10 | 1155.72 | (–0.07, –0.03) |
| School of Design | 0.15a | 0.02 | 9.28 | 1539.20 | (0.11, 0.18) |
| Faculty of Health | 0.24a | 0.02 | 13.21 | 1491.89 | (0.20, 0.28) |
| Faculty of Science & Horticulture | –0.06a | 0.01 | –4.14 | 1402.14 | (–0.08, –0.03) |
| Course Level 2 | 0.04a | 0.01 | 3.55 | 1248.46 | (0.02, 0.07) |
| Course Level 3 | 0.01a | 0.01 | 8.23 | 1328.22 | (0.07, 0.12) |
| Course Level 4 | 0.15a | 0.01 | 11.24 | 1356.55 | (0.13, 0.18) |
| Course Level 5 | 0.16a | 0.02 | 6.63 | 1117.37 | (0.11, 0.21) |
| Course Level 6 | 0.25a | 0.04 | 6.82 | 1140.22 | (0.18, 0.32) |
| sd Intercept | 0.13 | ||||
| cor Intercept & ZTC Status | 0.02 | ||||
| sd ZTC Status | 0.05 | ||||
| sd Residual | 0.17 |
[i] Note: SE = standard error; df = degrees of freedom; 95%CI = lower and upper confidence limits for 95% confidence intervals; aEstimates are statistically significant at p < .001; bEstimates are statistically significant at p < .01.
Table 5
Multilevel Regression Output for Outcome: DFW Rate (Possible Range 0–1).
| PARAMETERS | ESTIMATE | SE | STATISTIC | DF | 95% CI |
|---|---|---|---|---|---|
| Intercept | 0.20a | 0.01 | 29.34 | 1439.09 | (0.18, 0.21) |
| ZTC Status = 1 | –0.01 | 0.01 | –1.76 | 366.83 | (–0.02, 0.00) |
| Academic Year 19/20 | –0.02a | 0.00 | –4.95 | 12451.84 | (–0.02, –0.01) |
| Academic Year 20/21 | –0.01 | 0.00 | –1.58 | 12443.43 | (–0.01, 0.00) |
| Academic Year 21/22 | 0.02 | 0.00 | 6.03 | 12542.06 | (0.01, 0.03) |
| Spring Semester | –0.00 | 0.00 | –1.55 | 13127.25 | (–0.01, 0.00) |
| Summer Semester | –0.03a | 0.00 | –9.60 | 12950.47 | (–0.04, –0.03) |
| School of Business | 0.01 | 0.01 | 1.16 | 1151.94 | (–0.01, 0.03) |
| School of Design | –0.10a | 0.01 | –9.86 | 1728.34 | (–0.13, –0.08) |
| Faculty of Health | –0.13a | 0.01 | –10.69 | 1591.69 | (–0.15, –0.11) |
| Faculty of Science & Horticulture | 0.04 | 0.01 | 4.71 | 1473.50 | (0.02, 0.06) |
| Course Level 2 | –0.04a | 0.01 | –5.48 | 1284.07 | (–0.06, –0.03) |
| Course Level 3 | –0.07a | 0.01 | –9.29 | 1383.45 | (–0.09, –0.06) |
| Course Level 4 | –0.10a | 0.01 | –11.38 | 1423.78 | (–0.12, –0.09) |
| Course Level 5 | –0.13a | 0.02 | –8.05 | 1127.72 | (–0.16, –0.01) |
| Course Level 6 | –0.17a | 0.02 | –7.19 | 1165.43 | (–0.22, –0.12) |
| sd Intercept | 0.081 | ||||
| cor Intercept & ZTC Status | –0.04 | ||||
| sd ZTC Status | 0.03 | ||||
| sd Residual | 0.13 |
[i] Note: SE = standard error; df = degrees of freedom; 95%CI = lower and upper confidence limits for 95% confidence intervals; aEstimates are statistically significant at p < .001; bEstimates are statistically significant at p < .01.