Emilia Peytcheva is a senior survey methodologist at RTI International and an adjunct assistant professor at the University of North Carolina, Chapel Hill, USA. She holds a Ph.D. in survey methodology from the University of Michigan and has 25 years of experience designing and implementing surveys in different modes.Ting Yan is a Vice President at NORC at the University of Chicago, USA, and an adjunct research associate professor at the University of Maryland and University of Michigan, USA. She holds a Ph.D. in Survey Methodology from the University of Maryland and has more than 25 years of experience in questionnaire design and evaluation. She has published extensively on survey methodology.