Table 1 Descriptive and inferential statistics of the 25 included studies
# | Author(s) & year | OER type | Region | Subject | Educational level | Intervention duration | Sample size | Hedges’s g | SE | Sample | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
NE | NC | Total | ||||||||||
1 | Feldstein et al. (2012) | Interactive (text) book | North America | Business | Bachelor | 1 year | Large | 0.2 | 0.05 | 1394 | 2176 | 3750 |
2 | Hilton et al. (2013) | Interactive (text) book | North America | Mathematics | Bachelor | 1 semester | Large | − 0.09 | 0.30 | 2043 | 4164 | 6207 |
3 | Allen et al. (2015) | Interactive (text) book | North America | Chemistry | Bachelor | 1 trimester | Large | 0.02 | 0.07 | 377 | 348 | 725 |
4 | Robinson (2015) | Interactive course | North America | Varied | Post-secondary | 1 semester | Large | − 0.12 | 0.03 | 3254 | 10,819 | 14,073 |
5 | Hilton et al. (2016) | Interactive (text) book | North America | Varied | Bachelor | 1 trimester | Large | 0.12 | 0.03 | 2014 | 43,223 | 45,237 |
6 | Kelly and Rutherford (2017) | Interactive course | North America | Mathematics | Secondary | 1 month | Small | 0.19 | 0.21 | 39 | 52 | 91 |
7 | Chiorescu (2017) | Interactive (text) book | North America | Mathematics | Bachelor | 1 semester | Large | 0.20 | 0.14 | 159 | 447 | 606 |
8 | Choi and Carpenter (2017) | Interactive (text) book | North America | Computer science | Bachelor | 1 semester | Large | − 0.44 | 0.12 | 175 | 114 | 289 |
9 | Grewe and Davis (2017) | Interactive course | North America | History | Bachelor | 1 semester | Small | 1.10 | 0.20 | 58 | 60 | 118 |
10 | Gurung (2017) | Interactive (text) book | North America | Psychology | Bachelor | 1 week and less | Large | − 0.68 | 0.07 | 1228 | 982 | 2210 |
11 | Hendricks et al. (2017) | Interactive (text) book | North America | Physics | Bachelor | 1 semester | Large | 0.12 | 0.05 | 755 | 750 | 1505 |
12 | Westermann Juárez and Venegas Muggli (2017) | Interactive course | Latin America | Mathematics | Bachelor | 1 semester | Small | − 0.10 | 0.04 | 31 | 30 | 61 |
13 | Winitzky-Stephens and Pickavance (2017) | Document | North America | Varied | Bachelor | 1 week and less | Large | − 0.02 | 0.06 | 329 | 1120 | 1449 |
14 | Basu Mallick et al. (2018) | Interactive (text) book | North America | Varied | Bachelor | 1 semester | Large | − 0.14 | 0.02 | 4247 | 14,474 | 18,721 |
15 | Clinton (2018) | Interactive (text) book | North America | Psychology | Bachelor | 1 semester | Large | 0.23 | 0.09 | 204 | 316 | 520 |
16 | Colvard et al. (2018) | Interactive (text) book | North America | Varied | Bachelor | Not mentioned | Large | 0.21 | 0.01 | 10,141 | 11,681 | 21,822 |
17 | Jhangiani et al. (2018) | Interactive (text) book | North America | Psychology | Post-secondary | 1 semester | Small | 0.18 | 0.15 | 94 | 83 | 177 |
18 | Lawrence and Lester (2018) | Interactive (text) book | North America | Politics | Bachelor | 1 semester | Large | − 0.06 | 0.10 | 178 | 200 | 378 |
19 | Medley-Rath (2018) | Interactive (text) book | North America | Sociology | Bachelor | 1 week and less | Small | 0.08 | 0.29 | 23 | 24 | 47 |
20 | Engler and Shedlosky-Shoemaker (2019) | Interactive (text) book | North America | Psychology | Bachelor | 1 semester | Small | 0.00 | 0.28 | 24 | 25 | 49 |
21 | Grissett and Huffman (2019) | Interactive (text) book | North America | Psychology | Bachelor | 1 semester | Small | − 0.16 | 0.26 | 31 | 29 | 60 |
22 | Hardin et al. (2019) | Interactive (text) book | North America | Psychology | Bachelor | 1 week and less | Large | 0.22 | 0.06 | 507 | 1118 | 1625 |
23 | Shemy and Al-Habsi (2021) | Interactive course | Asia | Varied | Professional development | 1 week and less | Small | 2.29 | 0.41 | 20 | 20 | 40 |
24 | Sulisworo and Basriyah. (2021) | Video | Asia | Physics | Secondary | 1 week and less | Small | 0.20 | 0.28 | 26 | 26 | 52 |
25 | Harvey and Bond (2022) | Interactive (text) book | North America | Mathematics | Secondary | Not mentioned | Small | − 0.27 | 0.38 | 14 | 14 | 28 |