Table 2. Linear mixed effect models predicting readability scores by year and number of authors with journals as random effect.
FRE = Flesch Reading Ease; NDC = New Dale-Chall Readability Formula; df = Degrees of Freedom calculated using Satterthwaite approximation. signifies that abstracts with only 1 to 10 authors are included in the model.
| Metric | Subset | n | Random Effect | beta | CI 95% | t | df | p |
|---|---|---|---|---|---|---|---|---|
| FRE | Yes* | 652357 | Year | -0.17 | [-0.19, -0.14] | -11.3 | 122 | p<10-15 |
| Authors | -0.24 | [-0.26, -0.23] | -30.0 | 651832 | p <10-15 | |||
| No | 707250 | Year | -0.18 | [-0.21, -0.15] | -12.3 | 123 | p <10-15 | |
| Authors | -0.07 | [-0.08, -0.06] | -23.5 | 704922 | p<10-15 | |||
| NDC | Yes* | 652357 | Year | 0.014 | [0.012, 0.015] | 16.5 | 119 | p<10-15 |
| Authors | 0.033 | [0.032, 0.034] | 63.6 | 651516 | p <10-15 | |||
| No | 707250 | Year | 0.016 | [0.014, 0.017] | 19.6 | 118 | p <10-15 | |
| Authors | 0.008 | [0.007, 0.008] | 40.3 | 701014 | p <10-15 |