“…This approach is used by a number of researchers focusing on the contestants' performance (Stupurienė et al, 2016;Izu et al, 2017;Budinská et al, 2018;Bavera et al, 2020;Delal and Oner, 2020;van der Vegt and Schrijvers, 2013). A similar approach is determining the proportion of unsuccessful task solvers (Jašková and Kostová, 2020) and the proportion of task solvers who decided not to answer it. Vaníček (2016) or Vaníček and Šimandl (2020) found that the proportion of successful solvers and the proportion of solvers who decided not to answer are indicators of a task difficulty.…”