To be more specific they do work to filter out candidates that unambiguously lack the required skills. But for candidates that do have the required skills it's

To be more specific they do work to filter out candidates that unambiguously lack the required skills. But for candidates that do have the required skills it's more of a coim toss. Working through a coding question online filters out candidates that can't code or are not competent at coding. But for candidates who can code sufficiently well, it's kind of a coin toss. Maybe they just don't think of the solution in time and what not.