The DOI matches its Crossref record; 95 of the 98 references it cites were found in a registry or an index.
The Effectiveness of Online and Blended Learning: A Meta-Analysis of the Empirical Literature
Abstract
Background/Context: Earlier research on various forms of distance learning concluded that these technologies do not differ significantly from regular classroom instruction in terms of learning outcomes. Now that web-based learning has emerged as a major trend in both K–12 and higher education, the relative efficacy of online and face-to-face instruction needs to be revisited. The increased capabilities of web-based applications and collaboration technologies and the rise of blended learning models combining web-based and face-to-face classroom instruction have raised expectations for the effectiveness of online learning. Purpose/Objective/Research Question/Focus of Study: This meta-analysis was designed to produce a statistical synthesis of studies contrasting learning outcomes for either fully online or blended learning conditions with those of face-to-face classroom instruction. Population/Participants/Subjects: The types of learners in the meta-analysis studies were about evenly split between students in college or earlier years of education and learners in graduate programs or professional training. The average learner age in a study ranged from 13 to 44. Intervention/Program/Practice: The meta-analysis was conducted on 50 effects found in 45 studies contrasting a fully or partially online condition with a fully face-to-face instructional condition. Length of instruction varied across studies and exceeded one month in the majority of them. Research Design: The meta-analysis corpus consisted of (1) experimental studies using random assignment and (2) quasi-experiments with statistical control for preexisting group differences. An effect size was calculated or estimated for each contrast, and average effect sizes were computed for fully online learning and for blended learning. A coding scheme was applied to classify each study in terms of a set of conditions, practices, and methodological variables. Findings/Results: The meta-analysis found that, on average, students in online learning conditions performed modestly better than those receiving face-to-face instruction. The advantage over face-to-face classes was significant in those studies contrasting blended learning with traditional face-to-face instruction but not in those studies contrasting purely online with face-to-face conditions. Conclusions/Recommendations: Studies using blended learning also tended to involve additional learning time, instructional resources, and course elements that encourage interactions among learners. This confounding leaves open the possibility that one or all of these other practice variables contributed to the particularly positive outcomes for blended learning. Further research and development on different blended learning models is warranted. Experimental research testing design principles for blending online and face-to-face instruction for different kinds of learners is needed.
Overview
Integrity signals
Registry
Cites
Statistics
Verification
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
In the citing paper
“Existing meta-analyses tend to support the idea that either the academic performance of students –as final course grades– in online learning is higher than in face-to-face courses, or there are no significant differences between both.”
From Emergency remote teaching and students’ academic performance in higher education during the COVID-19 pandemic: A case study (2021) · cites this paper as Means et al., 2013
Citations
Cites
Borenstein, M., Hedges, L. V., Higgins, J. P. T., & Rothstein, H. R. (2009) · doi:10.1002/9780470743386 · Cited by 14,225
(1999) · Cited by 12,812
Wasserman, S. S., Hedges, L. V., & Olkin, I. (1988) · Journal of Educational Statistics · doi:10.2307/1164953 · Cited by 10,377
Borenstein, M., Hedges, L. V., Higgins, J. P. T., & Rothstein, H. R. (2021) · doi:10.1002/9781119558378 · Cited by 9,799
(2000) · Cited by 9,198
Cohen, J. (1992) · Psychological Bulletin · doi:10.1037//0033-2909.112.1.155 · Cited by 8,771
Reconsidering Research on Learning from Media
Clark, R. E. (1983) · Review of Educational Research · doi:10.3102/00346543053004445 · Cited by 2,715
The Handbook of Blended Learning: Global Perspectives, Local Designs
Bonk, C. J., Graham, C. R., Cross, J., & Moore, M. G. (2005) · Cited by 2,584
Meta-analysis of psychotherapy outcome studies.
Smith, M. L., & Glass, G. V. (1977) · American Psychologist · doi:10.1037/0003-066x.32.9.752 · Cited by 2,154
Blended learning systems: Definition, current trends, and future directions
Graham, C. R. (2006) · Cited by 1,767
Bernard, R. M., Abrami, P. C., Lou, Y., Borokhovski, E., Wade, A., Wozney, L., Wallet, P. A., Fiset, M., & Huang, B. (2004) · Review of Educational Research · doi:10.3102/00346543074003379 · Cited by 1,761
Zhang, D., Zhou, L., Briggs, R. O., & Nunamaker, J. F. (2005) · Information & Management · doi:10.1016/j.im.2005.01.004 · Cited by 1,286
Teaching Courses Online: A Review of the Research
Tallent-Runnels, M. K., Thomas, J. A., Lan, W. Y., Cooper, S., Ahern, T. C., Shaw, S. M., & Liu, X. (2006) · Review of Educational Research · doi:10.3102/00346543076001093 · Cited by 1,267
Disrupting class: how disruptive innovation will change the way the world learns
(2009) · Choice Reviews Online · doi:10.5860/choice.46-3377 · Cited by 1,001
Estimation of a Single Effect Size: Parametric and Nonparametric Methods
Hedges, L. V., & Olkin, I. (1985) · Statistical Methods for Meta-Analysis · doi:10.1016/b978-0-08-057065-5.50010-5 · Cited by 983
Espinosa, J. C. (2004) · Cited by 939
THE COMPARATIVE EFFECTIVENESS OF WEB‐BASED AND CLASSROOM INSTRUCTION: A META‐ANALYSIS
Sitzmann, T., Kraiger, K., STEWART, D., & Wisher, R. A. (2006) · Personnel Psychology · doi:10.1111/j.1744-6570.2006.00049.x · Cited by 812
Staying the course: online education in the United States, 2008
Allen, I. E., & Seaman, J. (2008) · Cited by 745
Proceedings of the 31st Annual Conference of the Cognitive Science Society.
Tamariz, M. (2009) · Cited by 638
Zhao, Y., Lei, J., Lai, B. Y. C., & Tan, H. S. (2005) · Teachers College Record: The Voice of Scholarship in Education · doi:10.1111/j.1467-9620.2005.00544.x · Cited by 618
Transforming American Education: Learning Powered by Technology
Peters, M. A., & Araya, D. (2011) · E-Learning and Digital Media · doi:10.2304/elea.2011.8.2.102 · Cited by 586
The Blended Learning Book: Best Practices, Proven Methodologies, and Lessons Learned
Bersin, J. (2004) · Cited by 528
Learning on Demand: Online Education in the United States, 2009.
Allen, I. E., & Seaman, J. (2010) · Cited by 520
Allen, I. E., & Seaman, J. (2003) · Issue Lab (Candid) · Cited by 409
The effectiveness of interactive distance education technologies in K-12 learning: A meta-analysis
Cavanaugh, T. (2001) · International journal of educational telecommunications · Cited by 391
(2004) · Cited by 377
Zacharia, Z. C. (2007) · Journal of Computer Assisted Learning · doi:10.1111/j.1365-2729.2006.00215.x · Cited by 347
Fifth generation distance education
Taylor, J. C. (2001) · University of Southern Queensland ePrints (University of Southern Queensland) · Cited by 340
(2007) · RePEc: Research Papers in Economics · Cited by 334
Self-citationA co-evolutionary model for supporting the emergence of authenticity
Barab, S. A., Squire, K. D., & Dueber, W. (2000) · Educational Technology Research and Development · doi:10.1007/bf02313400 · Cited by 312
Interactive Multimedia-Based E-Learning: A Study of Effectiveness
Zhang, D. (2005) · American Journal of Distance Education · doi:10.1207/s15389286ajde1903_3 · Cited by 282
The Hybrid Online Model: Good Practice
Martyn, M. (2003) · The EDUCAUSE quarterly/EDUCAUSE quarterly · Cited by 276
Schwen, T. M., & Hara, N. (2004) · Cambridge University Press eBooks · doi:10.1017/cbo9780511805080.010 · Cited by 265
Community of Practice: A Metaphor for Online Design?
Schwen, T. M., & Hara, N. (2003) · The Information Society · doi:10.1080/01972240309462 · Cited by 214
Riel, M. M., & Polin, L. G. (2004) · Cambridge University Press eBooks · doi:10.1017/cbo9780511805080.006 · Cited by 207
EL‐Deghaidy, H., & Nouby, A. M. (2007) · Computers & Education · doi:10.1016/j.compedu.2007.10.001 · Cited by 207
Collaborative learning through computer-mediated communication in academic education
Veerman, A. L., & Veldhuis-Diermanse, A. E. (2001) · Socio-Environmental Systems Modeling · Cited by 203
Keeping Pace with K-12 Online Learning: A Review of State-Level Policy and Practice, 2008.
Watson, J., Gemin, B., & Ryan, J. L. (2008) · Cited by 202
Ocker, R. J., & Yaverbaum, G. J. (1999) · Group Decision and Negotiation · doi:10.1023/a:1008621827601 · Cited by 182
K–12 ONLINE LEARNING: A SURVEY OF U.S. SCHOOL DISTRICT ADMINISTRATORS
Picciano, A. G., & Seaman, J. (2019) · Online Learning · doi:10.24059/olj.v11i3.1719 · Cited by 180
A meta‐analysis of the effectiveness of telecourses in distance education
Machtmes, K. L., & Asher, J. W. (2000) · American Journal of Distance Education · doi:10.1080/08923640009527043 · Cited by 174
2004 State of the Industry Report
Murphy, M. (2004) · American Water Works Association · doi:10.1002/j.1551-8833.2004.tb10759.x · Cited by 171
Nguyen, H. Q., Donesky, D., Wolpin, S. E., Reinke, L. F., Benditt, J. O., Paul, S. M., & Carrieri‐Kohlman, V. (2008) · Journal of Medical Internet Research · doi:10.2196/jmir.990 · Cited by 168
Effectiveness of e-learning in continuing medical education for occupational physicians
Hugenholtz, N. I. R., Croon, E. M. D., Smits, P. B. A., van Dijk, F. J. H., & Nieuwenhuijsen, K. (2008) · Occupational Medicine · doi:10.1093/occmed/kqn053 · Cited by 153
Frederickson, N. L., Reed, P., & Clifford, V. (2005) · Higher Education · doi:10.1007/s10734-004-6370-0 · Cited by 144
Pressure ulcers: e‐learning to improve classification by nurses and nursing students
Beeckman, D., Schoonhoven, L., Boucqué, H., Maele, G. V., & Defloor, T. (2008) · Journal of Clinical Nursing · doi:10.1111/j.1365-2702.2007.02200.x · Cited by 140
Çavuş, N., Uzunboylu, H., & İbrahim, D. (2007) · Journal of Educational Computing Research · doi:10.2190/t728-g676-4n18-6871 · Cited by 139
An interactive web-based curriculum on evidence-based medicine: design and effectiveness.
Schilling, K., Wiecha, J., Polineni, D., & Khalil, S. (2006) · PubMed · Cited by 127
A Study of the Effectiveness of the Louisiana Algebra I Online Course
O’Dwyer, L. M., Carey, R., & Kleiman, G. M. (2007) · Journal of Research on Technology in Education · doi:10.1080/15391523.2007.10782484 · Cited by 126
Englert, C. S., Zhao, Y., Dunsmore, K., Collings, N. Y., & Wolbers, K. A. (2007) · Learning Disability Quarterly · doi:10.2307/30035513 · Cited by 125
Online Professional Development for Teachers: Emerging Models and Methods.
DEDE, C. J. (2006) · doi:10.14507/er.v0.735 · Cited by 124
Online professional development for teachers: emerging models and methods
(2007) · Choice Reviews Online · doi:10.5860/choice.44-3983 · Cited by 118
Online Learning: From Information Dissemination to Fostering Collaboration
Barab, S. A., Thomas, M. K., & Merrill, H. S. (2001) · Cited by 109
Jang, K.-S., Hwang, S. Y., Park, S. J., Kim, Y. M., & Kim, M. J. (2005) · Journal of Nursing Education · doi:10.3928/01484834-20050101-07 · Cited by 108
The Effects of Web‐Based Learning on Struggling EFL College Writers
Al-Jarf, R. (2004) · Foreign Language Annals · doi:10.1111/j.1944-9720.2004.tb02172.x · Cited by 102
Multimedia comprehension skill predicts differential outcomes of web-based and lecture courses.
Maki, W. S., & Maki, R. H. (2002) · Journal of Experimental Psychology Applied · doi:10.1037//1076-898x.8.2.85 · Cited by 101
Do No Harm—A Comparison of the Effects of On-Line vs. Traditional Delivery Media on a Science Course
Schoenfeld-Tacher, R. M., McConnell, S. L., & Graham, M. (2001) · Journal of Science Education and Technology · doi:10.1023/a:1016690600795 · Cited by 94
Online Professional Development for Teachers
Vrasidas, C., & Gene, V. G. (2004) · Emerald Group Publishing Limited eBooks · doi:10.1108/978-1-60752-924-8 · Cited by 85
Online Compared to Face-to-Face Teacher Preparation for Learning Standards-Based Planning Skills
Peterson, C. L., & Bond, N. (2004) · Journal of Research on Technology in Education · doi:10.1080/15391523.2004.10782419 · Cited by 79
Two Peas in a Pod? A Comparison of Face-to-Face and Web Based Classrooms
Mentzer, G. A., Cryan, J. R., & Teclehaimanot, B. (2007) · The Journal of Technology and Teacher Education · Cited by 75
Pearson, P. D., Ferdig, R. E., & Blomeyer, R. (2005) · Cited by 73
The Collaboration Principle in Multimedia Learning
Jonassen, D. H., Lee, C. B., Yang, C.-C., & Laffey, J. M. (2005) · Cambridge University Press eBooks · doi:10.1017/cbo9780511816819.017 · Cited by 72
Online vs live methods for teaching difficult airway management to anesthesiology residents
Bello, G., Pennisi, M. A., Maviglia, R., Maggiore, S. M., Bocci, M. G., Montini, L. M., & Antonelli, M. M. (2005) · Intensive Care Medicine · doi:10.1007/s00134-005-2561-0 · Cited by 65
Carter, P. A. (2011) · Studies in Continuing Education · doi:10.1080/0158037x.2011.609668 · Cited by 64
Are Computer-Assisted Teaching Methods Effective?
DeBord, K. A., Aruguete, M. S., & Muhlig, J. (2004) · Teaching of Psychology · doi:10.1207/s15328023top3101_13 · Cited by 57
Harris, J. M., Elliott, T. E., Davis, B. E., Chabal, C., Fulginiti, J. V., & Fine, P. G. (2008) · Pain Medicine · doi:10.1111/j.1526-4637.2007.00399.x · Cited by 56
Learning in cyberspace:shaping the future
Gilliver, R. S., Randall, B., & Pok, Y. M. (1998) · Journal of Computer Assisted Learning · doi:10.1046/j.1365-2729.1998.143058.x · Cited by 55
Benjamin, S. E., Tate, D. F., Bangdiwala, S. I., Neelon, B., Ammerman, A. S., Dodds, J. M., & Ward, D. S. (2007) · Maternal and Child Health Journal · doi:10.1007/s10995-007-0277-1 · Cited by 54
Schmeeckle, J. M. (2003) · Journal of Science Education and Technology · doi:10.1023/a:1025028806189 · Cited by 53
E-learning: a comparative study for knowledge apprehension among nurses
Padalino, Y., & Peres, H. H. C. (2007) · Revista Latino-Americana de Enfermagem · doi:10.1590/s0104-11692007000300006 · Cited by 52
Multimedia comprehension skill predicts differential outcomes of web-based and lecture courses.
Maki, W. S., & Maki, R. H. (2002) · Journal of Experimental Psychology Applied · doi:10.1037/1076-898x.8.2.85 · Cited by 51
Day, T. M., Raven, M. R., & Newman, M. E. (1998) · Journal of Agricultural Education · doi:10.5032/jae.1998.04065 · Cited by 50
Evaluation of an Interactive Tutorial for Teaching Hypothesis Testing Concepts
Aberson, C. L., Berger, D. E., Healy, M. R., & Romero, V. L. (2003) · Teaching of Psychology · doi:10.1207/s15328023top3001_12 · Cited by 45
Evaluation of a Particle Repositioning Maneuver Web‐Based Teaching Module
Beyea, J. A., Wong, E. Y. L., Bromwich, M. A., Weston, W. W., & Fung, K. (2008) · The Laryngoscope · doi:10.1097/mlg.0b013e31814b290d · Cited by 45
Smith, M. S. (2009) · Science · doi:10.1126/science.1168018 · Cited by 44
Distance Education and Career and Technical Education: A Review of the Research Literature
Zirkle, C. (2003) · Journal of Vocational Education Research · doi:10.5328/jver28.2.161 · Cited by 40
Bethel, E. C., & Bernard, R. M. (2010) · Distance Education · doi:10.1080/01587919.2010.513950 · Cited by 34
The Future of Educational Technology.
Beckwith, D. (1988) · Canadian journal of educational communication · Cited by 33
Turner, M. K., Simon, S. R., Facemyer, K. C., Newhall, L. M., & Veach, T. L. (2006) · Teaching and Learning in Medicine · doi:10.1207/s15328015tlm1803_4 · Cited by 31
The Online Learning Imperative: A Solution to Three Looming Crises in Education.
Wise, B. (2010) · Education Digest: Essential Readings Condensed for Quick Review · Cited by 29
Achievement Predictors for a Computer-Applications Module Delivered Online
Wallace, P. E., & Clariana, R. B. (2000) · Journal of the Association for Information Systems · Cited by 26
Wang, L. (2008) · NSUWorks (Nova Southeastern University) · Cited by 25
Vandeweerd, J., Davies, J. C., Pinchbeck, G. L., & Cotton, J. C. (2007) · Journal of Veterinary Medical Education · doi:10.3138/jvme.34.2.160 · Cited by 23
Effects of a distance learning program on physicians' opioid- and benzodiazepine-prescribing skills
Midmer, D., Kahan, M., & Marlow, B. A. (2006) · Journal of Continuing Education in the Health Professions · doi:10.1002/chp.82 · Cited by 21
Developing Online Courses: A Comparison of Web-based Instruction with Traditional Instruction
O’Dell, M., Abbitt, J. T., Amos, D., & Davis, J. C. (1999) · Society for Information Technology & Teacher Education International Conference · Cited by 19
Technology‐based learning and the project manager
Ellis, R. C. T., Wood, G. D., & Thorpe, T. (2004) · Engineering Construction & Architectural Management · doi:10.1108/09699980410558557 · Cited by 17
Sexton, J. S., Raven, M. R., & Newman, M. E. (2002) · Journal of Agricultural Education · doi:10.5032/jae.2002.03025 · Cited by 17
Maloberti, F. (2013) · IEEE Solid-State Circuits Magazine · doi:10.1109/mssc.2013.2255493 · Cited by 13
The Effectiveness of Web-based Training
Wisher, R. A., & Olson, T. M. (2003) · PsycEXTRA Dataset · doi:10.1037/e500802012-001 · Cited by 13
Exploring the Academic Self within an Electronic Mail Environment
Spires, H. A., Mason, C., Crissman, C., & Jackson, A. Y. (2001) · Research in the Teaching of Developmental Education · Cited by 8
Employees' attitude toward e-learning: Implications for policy in industry environments
Hairston, N. R. (2007) · Cited by 7
Suter, W. N., & Perry, M. K. (1997) · Cited by 5
Forms of Synchronous Dialogue Resulting from Web-based Professional Development
Shotsberger, P. G. (1999) · Society for Information Technology & Teacher Education International Conference · Cited by 3
Using Data Mining Findings to Aid Searching for Better Cognitive Models
Feng, M., Heffernan, N. T., & Koedinger, K. R. (2010) · Lecture notes in computer science · doi:10.1007/978-3-642-13437-1_55 · Cited by 1
Research works printed but not linked: 23
- Barab S. A., 2001, Journal of Interactive Learning Research, 12, 105
- Bates A. W., 1997, Learning Quarterly, 2, 7
- Bhattacharya M., 1999, Proceedings of WebNet World Conference on the WWW and Internet 1999, 100
- *Caldwell E. R. (2006). A comparative study of three instructional modalities in a computer programming course: Traditional instruction, web-based instruction, and online instruction (Doctoral dissertation). Retrieved from ProQuest Dissertations and Theses database. (UMI No. AAT 3227694)
- Cavanaugh C., 2001, International Journal of Educational Telecommunications, 7, 73
- 10.1037/0033-2909.112.1.155 · DOI · Paper page
- Graham C. R., 2005, Handbook of blended learning: Global perspectives, local designs, 3
- Hermann F., 2001, European perspectives on computer-supported collaborative learning, 293
- Horn M. B., 2011, The rise of K-12 blended learning.
- Long M., 2005, ‘Does it work?’: The impact of technology and professional development on student achievement
- *Lowry A. E. (2007). Effects of online versus face-to-face professional development with a team-based learning community approach on teachers’ application of a new instructional practice (Doctoral dissertation). Retrieved from ProQuest Dissertations and Theses database. (UMI No. AAT 3262466)
- Mentzer G. A., 2007, Journal of Technology and Teacher Education, 15, 233
- National Survey of Student Engagement, 2008, Promoting engagement for all students: the imperative to look within.
- Parsad B., 2008, Distance education at degree-granting postsecondary institutions: 2006-07
- Rooney J. E., 2003, Association Management, 55, 26
- Schilling K., 2006, Family Medicine, 38, 126
- Schmeeckle J. M., 2003, Technology, 12, 205
- Shotsberger P. G., 1999, Proceedings of Society for Information Technology & Teacher Education International Conference 1999, 1777
- Smith R., 2005, A synthesis of new research on K-12 online learning
- Spires H. A., 2001, Research and Teaching in Developmental Education, 17, 5
- Wallace P. E., 2000, Journal of Information Systems Education, 11, 13
- Wang L., 2008, Journal of Educational Multimedia and Hypermedia, 17, 43
- What Works Clearinghouse, 2007, Technical details of WWC-conducted computations
Cited by
Sorted by citations
Blended learning: the new normal and emerging technologies
Dziuban, C., Graham, C. R., Moskal, P. D., Norberg, A., & Sicilia, N. (2018) · International Journal of Educational Technology in Higher Education · doi:10.1186/s41239-017-0087-5 · Cited by 1,252
Variables associated with achievement in higher education: A systematic review of meta-analyses.
Schneider, M., & Preckel, F. (2017) · Psychological Bulletin · doi:10.1037/bul0000098 · Cited by 1,347
Bernard, R. M., Borokhovski, E., Schmid, R. F., Tamim, R. M., & Abrami, P. C. (2014) · Journal of Computing in Higher Education · doi:10.1007/s12528-013-9077-3 · Cited by 870
It's not about seat time: Blending, flipping, and efficiency in active learning classrooms
Baepler, P., Walker, J. D., & Driessen, M. D. (2014) · Computers & Education · doi:10.1016/j.compedu.2014.06.006 · Cited by 883
Iglesias-Pradas, S., Hernández-García, Á., Chaparro-Peláez, J., & Prieto, J. L. (2021) · Computers in Human Behavior · doi:10.1016/j.chb.2021.106713 · Cited by 693
Metadata
- Authors
- Means, B., Toyama, Y., Murphy, R., & Baki, M.
- Affiliations
- SRI International (US)
- Venue
- Teachers College Record: The Voice of Scholarship in Education
- Publisher
- SAGE Publications
- Published
- 2013-03
- Volume
- 115
- Issue
- 3
- Pages
- 1-47
- ISSN
- 0040-0475 (ISSN-L)
- 0161-4681
- 1467-9620
- OpenAlex
- W1719359252
- Cited by
- 1,638
- References
- 98
- Citations by year
- 2026: 176 · 2025: 203 · 2024: 160 · 2023: 188 · 2022: 166 · 2021: 208 · 2020: 152 · 2019: 108 · 2018: 95 · 2017: 59 · 2016: 51 · 2015: 45 · 2014: 22 · 2013: 4
- FWCI
- 28.64
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Teachers College Record The Voice of Scholarship in Education (publishedVersion)
- Topics
- Social Sciences › Education › Online and Blended Learning
- Social Sciences › Education › Online Learning Methods and Innovations
- Social Sciences › Education › Technology-Enhanced Education Studies
- Keywords
- online learning, blended learning, face-to-face teaching, learning outcomes, distance education, web-based learning, teaching effectiveness, effect size, K-12 education, higher education, professional training, student interaction
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review