Review
BibTex RIS Cite

Comparative Examination of Exams Used in Applying to Postgraduate Programs: The Case of GRE, GMAT and ALES

Year 2025, Volume: 54 Issue: 247, 1801 - 1832, 01.08.2025

Tansu Alan , Seher Yalçın

https://doi.org/10.37669/milliegitim.1577420

Abstract

In Türkiye, the Academic Staff and Graduate Education Entrance Exam (ALES) is widely used for admission to graduate programs, while internationally, the Graduate Record Examination (GRE) and the Graduate Management Admission Test (GMAT) are preferred. Given that ALES, GMAT, and GRE are key exams used to measure academic and professional success, this study aims to compare these exams based on their purpose, subtests, scaling, psychometric properties, test security, test theory, and administration methods. Conducted as a case study within qualitative research methods, a comprehensive literature review was performed, and a comparative analysis was used to evaluate the data obtained.The results indicate that ALES comprises subtests that assess similar skills to those measured by GRE and GMAT and employs comparable reliability methods. However, it was also found that ALES differs from GRE and GMAT in terms of its administration and underlying test theory. To elevate ALES to international test standards similar to GRE and GMAT, this study recommends implementing test equating and bias analysis in its development process, as well as introducing computer-based adaptive testing based on item response theory. These steps can help transform ALES into an exam with more standardized testing conditions, thereby contributing to a more valid and reliable assessment of candidates.

Keywords

Graduate education ALES GRE GMAT

References

  • Aliustaoğlu, F., ve Tuna, A. (2016). Akademik personel ve lisansüstü eğitimi giriş sınavı (ALES) matematik sorularının MATH taksonomisine göre analizi. Trakya Üniversitesi Eğitim Fakültesi Dergisi, 6(2), 126-137. https://dergipark.org.tr/tr/pub/trkefd/issue/24152/256284
  • Arapgirlioğlu, H., Zahal, O., Gürpınar, E. ve Özhan, U. (2014). Lisansüstü programlara başvuran adayların ALES, yabancı dil ve mezuniyet not ortalamaları arasındaki ilişkiler (İnönü Üniversitesi Eğitim Bilimleri Enstitüsü Örneği). İnönü Üniversitesi Eğitim Bilimleri Enstitüsü Dergisi, 1(1), 30-40. https://dergipark.org.tr/tr/pub/inujgse/issue/8717/108866
  • Baker, F. B. (2001). The basics of item response theory. ERIC Clearinghouse on Assessment and Evaluation.
  • Bedsole, C. B. (2013). Apples to apples? comparing the predctive validity of the GMAT and GRE for business schools, and building a better admissions formula. [Unpublished doctoral dissertion]. The University of Georgia.
  • Bock, D.B., Muraki, E., & Pfeiffenberger, W. (1988). Item pool maintenance in the presence of item parameter drift. Journal of Educational Measurement, 25(4), 275-285. https://doi.org/10.1111/j.1745-3984.1988.tb00308.x
  • Bulut, O. (2015). Applying item response theory models to Entrance Examination for Graduate Studies: Practical issues and insights. Journal of Measurement and Evaluation in Education and Psychology, 6(2), 313-330. https://doi.org/10.21031/epod.17523
  • Coşkun, E. ve Tuna, A. (2021). ALES matematik sorularının MATH taksonomisine göre incelenmesi: 2006 –2013. Online Journal of Mathematics, Science and Technology Education (OJOMSTE),2(1), 43-54. https://www.ojomste.com/index.php/1
  • Desjardins, C. D., & Bulut, O. (2018). Handbook of educational measurement and psychometrics using R. Boca Raton, FL: CRC Press.
  • Donaldson, B. and McNicholas, C. (2004). Understanding the postgraduate education market for UK-based students: A review and empirical study. International Journal of Nonprofit and Voluntary Sector Marketing, 9(4), 288-379. https://doi.org/10.1002/nvsm.259
  • Embretson S. E., & Reise S. P. (2000). Item Response Theory for Psychologists. Mahwah, NJ: Lawrence Earlbaum.
  • Espinosa, M. P., & Gardeazabal, J. (2010). Optimal correction for guessing in multiple-choice tests. Journal of Mathematical Psychology, 54(5), 415–425. https://doi.org/10.1016/j.jmp.2010.06.002
  • Ercoşkun, M. (2020). Öğretmen adaylarının akademik ve ALES (Akademik Personel ve Lisansüstü Eğitimi Giriş Sınavı) başarı puanlarının incelenmesi. Akdeniz Eğitim Araştırmaları Dergisi, 14(33), 523-541. https://doi.org/10.29329/mjer.2020.272.24
  • ETS (2024). The GRE general test. Educational Testing Service. https://www.ets.org/gre/test-takers/general-test/schedule.html
  • ETS (2023). Guide to the use of scores. Educational Testing Service. https://www.ets.org/content/dam/ets-org/pdfs/gre/gre-guide-to-the-use-of-scores.pdf
  • ETS (2024). A Snapshot of the Individual Who Took the GRE Genel Test. https://www.ets.org/pdfs/gre/snapshot.pdf?utm_source
  • GMAT (2025). GMAT exam. Graduate Management Admission Council. https://www.mba.com
  • GMAT (2024). GMAT™ Geographic Trend Report: Testing Year 2023. https://www.mba.com/-/media/files/gmac/research/geographic-trends/gmat-geographic-trend-report-testing-year-2023-pdf.pdf
  • Hambleton, R., Swaminathan, R., & Rogers, H.J. (1991). Fundementals of Item Response Theory. California: Sage Pub.
  • Karaman, S. ve Bakırcı, F. (2010). Türkiye’de lisansüstü eğitim: Sorunlar ve çözüm önerileri. Sosyal Bilimler Araştırmaları Dergisi, 2, 94-114. https://dergipark.org.tr/tr/pub/gopsbad/issue/48557/616554
  • Kearney, M. L. (2008). The role of post-graduate education in research systems. UNESCO/DCU workshop on trends in post-graduate education (Dublin City University, 5-7 March 2008).
  • Kelecioğlu, H. (1994). Öğrenci seçme sınavı puanlarının eşitlenmesi üzerine bir çalışma. [Yayımlanmamış doktora tezi]. Hacettepe Üniversitesi.
  • Klieger, D.M., Cline, F.A., Holtzman, S.L., Minsky, J.L. & Lorenz, F. (2014). New perspectives on the validity of the GRE general test for predicting graduate school grades. ETS Research Report Series, 1-62. https://doi.org/10.1002/ets2.12026
  • Koys, D. (2005). The validity of the Graduate Management Admission Test for non-U.S. students. Journal of Education for Business, 80, 236–239.
  • Kuncel, N., Crede, M., & Thomas, L. (2007). A meta-analysis of the predictive validity of the Graduate Management Admission Test (GMAT) and undergraduate grade point average (UGPA) forgraduate student academic performance. Academy of Management Learning and Education, 6, 61-68. https://doi.org/10.5465/amle.2007.24401702
  • Kurysheva, A., Dilaver, G., Fox, C.M., Kell, H., Kern, M.R., L. & van Rijen, H.V.M. (2024). To test or not to test? The Graduate Record Examinations: Predictive validity toward graduate study success on research masters’ programs in a large European University. Education Sciences, 14, 549. https://doi.org/10.3390/educsci14050549
  • Lord, F.M. (1980). Applications of ıtem response theory to practical testing problems. Lawrence Erlbaum Associates Publishers.
  • Mutluer, C., L. & Nartgün, Z. (2017). Test equating study concerning to ALES (Academıc Personnel And Postgraduate Education Entrance Exam) scores obtained at different times in a year. European Journal of Education Studies, 3(12), 96-120. http://dx.doi.org/10.46827/ejes.v0i0.1270
  • MBA (2024). Evolving the score scale with the GMAT™ focus edition. https://www.mba.com/exams-and-exam-prep/gmat-exam/gmat-focus-evolving-score-scale
  • Örnek, E. (2002). Hacettepe Üniversitesi Sosyal Bilimler Enstitüsüne bağlı yüksek lisans programlarındaki öğrencilerin lisansüstü eğitimi giriş sınavı puanları ile akademik başarıları arasındaki ilişkiler [Yayımlanmamış yüksek lisans tezi]. Hacettepe Üniversitesi
  • ÖSYM (2018a). 2017 ALES sonbahar değerlendirme raporu. https://dokuman.osym.gov.tr/pdfdokuman/2018/GENEL/ALESRaporu_13022018.pdf
  • ÖSYM (2018b). 2018 ALES/2 değerlendirme raporu. https://dokuman.osym.gov.tr/pdfdokuman/2018/GENEL/ales2degrapor24122018.pdf
  • ÖSYM (2024). ÖSYM resmî sitesi. https://www.osym.gov.tr/
  • Öztürk, N., ve Anıl, D. (2012). Akademik personel ve lisansüstü eğitimi giriş sınavı puanlarının eşitlenmesi üzerine bir çalışma. Eğitim ve Bilim, 37(165), 180-193. https://egitimvebilim.ted.org.tr/index.php/EB/article/view/1141/421
  • Powers, D. E. (2004). Validity of Graduate Record Examinations (GRE) general test scores for admissions to Colleges of Veterinary Medicine. Journal of Applied Psychology, 89(2), 208–219. https://doi.org/10.1037/0021-9010.89.2.208
  • Reckase, M.D. (2011). Computerized adaptive assessment (CAA): The way forward. In The road ahead for state assessments, policy analysis for California education and Rennie Center for Education Research & Policy (pp.1-11). Rennie Center for Education Research & Policy.
  • Robin, F., & Zhao, C. (2014). Timing of the analytical writing measure of the GRE revised general test. The Research Foundation for the GRE revised General Test: A compendium of studies. (C. Wendler, B. Bridgeman, & C. Ezzo, Eds.). Educational Testing Service.
  • Rotou, O., Patsula, L., Steffen, M., & Rizavi, S. (2007). Comparison of multistage tests with computerized adaptive and paper-and-pencil tests. ETS, Research Report.
  • Rudner, L. M. (2012). Demystifying the GMAT: computer-based testing terms. Graduate Management Admission Council.
  • Schrader, W. B. (1984). The Graduate Management Admission Test: Technical report on test development and score interpretation for GMAT users. Educational Testing Services. https://files.eric.ed.gov/fulltext/ED251483.pdf
  • Segall, D. O. (2005). Computerized adaptive testing. Encyclopedia of Social Measurement, 1, 429–438.
  • Stocking, M. L., & Lewis, C. (1995). A new method of controlling item exposure in computerized adaptive testing. ETS Research Report Series, 1995(2), i–29. https://doi.org/10.1002/j.2333-8504.1995.tb01660.x
  • Talento-Miller, E. (2005). GMAT validity for six european MBA programs. GMAC Research Reports, RR-05-07.
  • Talento-Miller, E. (2008). Generalizability of GMAT validity to programs outside the U.S. International Journal of Testing, 8, 127–142. https://doi.org/10.1080/15305050802001193
  • Tokat, E. (2004). Lisansüstü eğitimi giriş sınavı ve diğer kabul ölçülerinin yordama geçerliğine ilişkin bir araştırma [Yayımlanmamış yüksek lisans tezi]. Ankara Üniversitesi
  • Wilson, K. M. (1982). GMAT and GRE aptitude test performance’ in relation to primary language and scores on TOEFL. ETS Research Report Series. https://doi.org/10.1002/j.2333-8504.1982.tb01314.x.
  • Yıldırım, A. ve Şimşek, H. (2020). Sosyal bilimlerde nitel araştırma yöntemleri. Seçkin Yayıncılık.
  • Yükseköğretim Kurulu (YÖK). (2025). Yükseköğretim istatistikleri. https://istatistik.yok.gov.tr

Lisansüstü Programlara Başvuruda Kullanılan Sınavların Karşılaştırmalı İncelenmesi: GRE, GMAT ve ALES Örneği

Year 2025, Volume: 54 Issue: 247, 1801 - 1832, 01.08.2025

Tansu Alan , Seher Yalçın

https://doi.org/10.37669/milliegitim.1577420

Abstract

Türkiye'de lisansüstü programlara başvurularda yaygın olarak Akademik Personel ve Lisansüstü Eğitimi Giriş Sınavı (ALES) kullanılırken, uluslararası düzeyde Lisansüstü Eğitim Giriş Sınavı [Graduate Record Examination (GRE)] ve Lisansüstü Yönetim Kabul Sınavı [Graduate Management Admission Test (GMAT)] tercih edilmektedir. ALES, GMAT ve GRE, akademik ve mesleki başarıyı ölçmek için kullanılan önemli sınavlar olmasından dolayı bu sınavların kullanım amacı, alt testleri, ölçeklenme şekli, psikometrik özellikleri, test güvenliği, test kuramı ve uygulanma şekli bakımından karşılaştırılmasını amaçlayan bu araştırma nitel araştırma yöntemlerinden durum çalışması olarak yürütülmüştür. Bu kapsamda alan yazın incelemesi yapılmış, elde edilen verilerin çözümlenmesinde karşılaştırmalı analiz yapılmıştır. Araştırma sonucunda, ALES’in GRE ve GMAT ile benzer becerileri ölçen benzer alt testlerden oluştuğu ve benzer güvenirlik yöntemlerinin kullanıldığı sonucuna ulaşılmıştır. Bunun yanı sıra ALES’in uygulanma şekli ve temel aldığı test kuramının GRE ve GMAT’ten farklı olduğu sonucuna ulaşılmıştır. Bu çalışmada, ALES'in GRE ve GMAT gibi uluslararası test standartlarına ulaşabilmesi için test geliştirme süreçlerinde test eşitleme ve yanlılık analizlerinin yapılması, ayrıca madde tepki kuramına dayalı bilgisayar tabanlı uyarlanabilir testlerin uygulanması önerilmektedir. Bu adımlar, ALES’in daha standart test koşullarını sağlayan bir sınav haline gelmesini mümkün kılarak, adayların daha geçerli ve güvenilir bir şekilde değerlendirilmesine katkıda bulunabilir.

Keywords

Lisansüstü eğitim ALES GRE GMAT

References

  • Aliustaoğlu, F., ve Tuna, A. (2016). Akademik personel ve lisansüstü eğitimi giriş sınavı (ALES) matematik sorularının MATH taksonomisine göre analizi. Trakya Üniversitesi Eğitim Fakültesi Dergisi, 6(2), 126-137. https://dergipark.org.tr/tr/pub/trkefd/issue/24152/256284
  • Arapgirlioğlu, H., Zahal, O., Gürpınar, E. ve Özhan, U. (2014). Lisansüstü programlara başvuran adayların ALES, yabancı dil ve mezuniyet not ortalamaları arasındaki ilişkiler (İnönü Üniversitesi Eğitim Bilimleri Enstitüsü Örneği). İnönü Üniversitesi Eğitim Bilimleri Enstitüsü Dergisi, 1(1), 30-40. https://dergipark.org.tr/tr/pub/inujgse/issue/8717/108866
  • Baker, F. B. (2001). The basics of item response theory. ERIC Clearinghouse on Assessment and Evaluation.
  • Bedsole, C. B. (2013). Apples to apples? comparing the predctive validity of the GMAT and GRE for business schools, and building a better admissions formula. [Unpublished doctoral dissertion]. The University of Georgia.
  • Bock, D.B., Muraki, E., & Pfeiffenberger, W. (1988). Item pool maintenance in the presence of item parameter drift. Journal of Educational Measurement, 25(4), 275-285. https://doi.org/10.1111/j.1745-3984.1988.tb00308.x
  • Bulut, O. (2015). Applying item response theory models to Entrance Examination for Graduate Studies: Practical issues and insights. Journal of Measurement and Evaluation in Education and Psychology, 6(2), 313-330. https://doi.org/10.21031/epod.17523
  • Coşkun, E. ve Tuna, A. (2021). ALES matematik sorularının MATH taksonomisine göre incelenmesi: 2006 –2013. Online Journal of Mathematics, Science and Technology Education (OJOMSTE),2(1), 43-54. https://www.ojomste.com/index.php/1
  • Desjardins, C. D., & Bulut, O. (2018). Handbook of educational measurement and psychometrics using R. Boca Raton, FL: CRC Press.
  • Donaldson, B. and McNicholas, C. (2004). Understanding the postgraduate education market for UK-based students: A review and empirical study. International Journal of Nonprofit and Voluntary Sector Marketing, 9(4), 288-379. https://doi.org/10.1002/nvsm.259
  • Embretson S. E., & Reise S. P. (2000). Item Response Theory for Psychologists. Mahwah, NJ: Lawrence Earlbaum.
  • Espinosa, M. P., & Gardeazabal, J. (2010). Optimal correction for guessing in multiple-choice tests. Journal of Mathematical Psychology, 54(5), 415–425. https://doi.org/10.1016/j.jmp.2010.06.002
  • Ercoşkun, M. (2020). Öğretmen adaylarının akademik ve ALES (Akademik Personel ve Lisansüstü Eğitimi Giriş Sınavı) başarı puanlarının incelenmesi. Akdeniz Eğitim Araştırmaları Dergisi, 14(33), 523-541. https://doi.org/10.29329/mjer.2020.272.24
  • ETS (2024). The GRE general test. Educational Testing Service. https://www.ets.org/gre/test-takers/general-test/schedule.html
  • ETS (2023). Guide to the use of scores. Educational Testing Service. https://www.ets.org/content/dam/ets-org/pdfs/gre/gre-guide-to-the-use-of-scores.pdf
  • ETS (2024). A Snapshot of the Individual Who Took the GRE Genel Test. https://www.ets.org/pdfs/gre/snapshot.pdf?utm_source
  • GMAT (2025). GMAT exam. Graduate Management Admission Council. https://www.mba.com
  • GMAT (2024). GMAT™ Geographic Trend Report: Testing Year 2023. https://www.mba.com/-/media/files/gmac/research/geographic-trends/gmat-geographic-trend-report-testing-year-2023-pdf.pdf
  • Hambleton, R., Swaminathan, R., & Rogers, H.J. (1991). Fundementals of Item Response Theory. California: Sage Pub.
  • Karaman, S. ve Bakırcı, F. (2010). Türkiye’de lisansüstü eğitim: Sorunlar ve çözüm önerileri. Sosyal Bilimler Araştırmaları Dergisi, 2, 94-114. https://dergipark.org.tr/tr/pub/gopsbad/issue/48557/616554
  • Kearney, M. L. (2008). The role of post-graduate education in research systems. UNESCO/DCU workshop on trends in post-graduate education (Dublin City University, 5-7 March 2008).
  • Kelecioğlu, H. (1994). Öğrenci seçme sınavı puanlarının eşitlenmesi üzerine bir çalışma. [Yayımlanmamış doktora tezi]. Hacettepe Üniversitesi.
  • Klieger, D.M., Cline, F.A., Holtzman, S.L., Minsky, J.L. & Lorenz, F. (2014). New perspectives on the validity of the GRE general test for predicting graduate school grades. ETS Research Report Series, 1-62. https://doi.org/10.1002/ets2.12026
  • Koys, D. (2005). The validity of the Graduate Management Admission Test for non-U.S. students. Journal of Education for Business, 80, 236–239.
  • Kuncel, N., Crede, M., & Thomas, L. (2007). A meta-analysis of the predictive validity of the Graduate Management Admission Test (GMAT) and undergraduate grade point average (UGPA) forgraduate student academic performance. Academy of Management Learning and Education, 6, 61-68. https://doi.org/10.5465/amle.2007.24401702
  • Kurysheva, A., Dilaver, G., Fox, C.M., Kell, H., Kern, M.R., L. & van Rijen, H.V.M. (2024). To test or not to test? The Graduate Record Examinations: Predictive validity toward graduate study success on research masters’ programs in a large European University. Education Sciences, 14, 549. https://doi.org/10.3390/educsci14050549
  • Lord, F.M. (1980). Applications of ıtem response theory to practical testing problems. Lawrence Erlbaum Associates Publishers.
  • Mutluer, C., L. & Nartgün, Z. (2017). Test equating study concerning to ALES (Academıc Personnel And Postgraduate Education Entrance Exam) scores obtained at different times in a year. European Journal of Education Studies, 3(12), 96-120. http://dx.doi.org/10.46827/ejes.v0i0.1270
  • MBA (2024). Evolving the score scale with the GMAT™ focus edition. https://www.mba.com/exams-and-exam-prep/gmat-exam/gmat-focus-evolving-score-scale
  • Örnek, E. (2002). Hacettepe Üniversitesi Sosyal Bilimler Enstitüsüne bağlı yüksek lisans programlarındaki öğrencilerin lisansüstü eğitimi giriş sınavı puanları ile akademik başarıları arasındaki ilişkiler [Yayımlanmamış yüksek lisans tezi]. Hacettepe Üniversitesi
  • ÖSYM (2018a). 2017 ALES sonbahar değerlendirme raporu. https://dokuman.osym.gov.tr/pdfdokuman/2018/GENEL/ALESRaporu_13022018.pdf
  • ÖSYM (2018b). 2018 ALES/2 değerlendirme raporu. https://dokuman.osym.gov.tr/pdfdokuman/2018/GENEL/ales2degrapor24122018.pdf
  • ÖSYM (2024). ÖSYM resmî sitesi. https://www.osym.gov.tr/
  • Öztürk, N., ve Anıl, D. (2012). Akademik personel ve lisansüstü eğitimi giriş sınavı puanlarının eşitlenmesi üzerine bir çalışma. Eğitim ve Bilim, 37(165), 180-193. https://egitimvebilim.ted.org.tr/index.php/EB/article/view/1141/421
  • Powers, D. E. (2004). Validity of Graduate Record Examinations (GRE) general test scores for admissions to Colleges of Veterinary Medicine. Journal of Applied Psychology, 89(2), 208–219. https://doi.org/10.1037/0021-9010.89.2.208
  • Reckase, M.D. (2011). Computerized adaptive assessment (CAA): The way forward. In The road ahead for state assessments, policy analysis for California education and Rennie Center for Education Research & Policy (pp.1-11). Rennie Center for Education Research & Policy.
  • Robin, F., & Zhao, C. (2014). Timing of the analytical writing measure of the GRE revised general test. The Research Foundation for the GRE revised General Test: A compendium of studies. (C. Wendler, B. Bridgeman, & C. Ezzo, Eds.). Educational Testing Service.
  • Rotou, O., Patsula, L., Steffen, M., & Rizavi, S. (2007). Comparison of multistage tests with computerized adaptive and paper-and-pencil tests. ETS, Research Report.
  • Rudner, L. M. (2012). Demystifying the GMAT: computer-based testing terms. Graduate Management Admission Council.
  • Schrader, W. B. (1984). The Graduate Management Admission Test: Technical report on test development and score interpretation for GMAT users. Educational Testing Services. https://files.eric.ed.gov/fulltext/ED251483.pdf
  • Segall, D. O. (2005). Computerized adaptive testing. Encyclopedia of Social Measurement, 1, 429–438.
  • Stocking, M. L., & Lewis, C. (1995). A new method of controlling item exposure in computerized adaptive testing. ETS Research Report Series, 1995(2), i–29. https://doi.org/10.1002/j.2333-8504.1995.tb01660.x
  • Talento-Miller, E. (2005). GMAT validity for six european MBA programs. GMAC Research Reports, RR-05-07.
  • Talento-Miller, E. (2008). Generalizability of GMAT validity to programs outside the U.S. International Journal of Testing, 8, 127–142. https://doi.org/10.1080/15305050802001193
  • Tokat, E. (2004). Lisansüstü eğitimi giriş sınavı ve diğer kabul ölçülerinin yordama geçerliğine ilişkin bir araştırma [Yayımlanmamış yüksek lisans tezi]. Ankara Üniversitesi
  • Wilson, K. M. (1982). GMAT and GRE aptitude test performance’ in relation to primary language and scores on TOEFL. ETS Research Report Series. https://doi.org/10.1002/j.2333-8504.1982.tb01314.x.
  • Yıldırım, A. ve Şimşek, H. (2020). Sosyal bilimlerde nitel araştırma yöntemleri. Seçkin Yayıncılık.
  • Yükseköğretim Kurulu (YÖK). (2025). Yükseköğretim istatistikleri. https://istatistik.yok.gov.tr
There are 47 citations in total.

Details

Primary Language Turkish
Subjects Measurement and Evaluation in Education (Other)
Journal Section Derleme Makalesi
Authors

Tansu Alan 0000-0001-5855-0302

Seher Yalçın 0000-0003-0177-6727

Publication Date August 1, 2025
Submission Date November 1, 2024
Acceptance Date May 15, 2025
Published in Issue Year 2025 Volume: 54 Issue: 247

Cite

APA Alan, T., & Yalçın, S. (2025). Lisansüstü Programlara Başvuruda Kullanılan Sınavların Karşılaştırmalı İncelenmesi: GRE, GMAT ve ALES Örneği. Milli Eğitim Dergisi, 54(247), 1801-1832. https://doi.org/10.37669/milliegitim.1577420
 Download Cover Image