Dr Abhaya Indrayan is the author of Medical Biostatistics (3rd ed. CRC Press) and former Professor and Chair of the Department of Biostatistics and Medical Informatics at Delhi University College of Medical Sciences, Delhi. Currently working as Biostatisitcs Consultant to Max Healthcare Institute, New Delhi, he has frequently provided biostatistical consultation to the World Health Organization, the World Bank and UNAIDS. Dr Indrayan has delivered the inaugural address at Biostatistics Workshop at Institute of Cytology and Preventive Oncology, NOIDA, been a Guest of Honor at Workshop on Designs and Sample Size at Postgraduate Institute of Medical Sciences and Research, Chandigarh, and has presented papers in more than 20 international conferences.