Why has this threshold been selected? This being a measure of the amount of time taken by a human to achieve the results 100% of the time, picking a 50% measure presents at least 2 problems:
(1) There may not be a direct linear connection between 50% achievement and 100%, such that it is valid to grade these two against each other directly (e.g. winning 50% of international soccer matches is orders of magnitude easier than winning 100% of them)
(2) The value of 100% achievement by humans may not reasonably be compared with 50% achievement in practical terms - if your car fails to start 50% of days you try,... (read more)
Why has this threshold been selected? This being a measure of the amount of time taken by a human to achieve the results 100% of the time, picking a 50% measure presents at least 2 problems:
(1) There may not be a direct linear connection between 50% achievement and 100%, such that it is valid to grade these two against each other directly (e.g. winning 50% of international soccer matches is orders of magnitude easier than winning 100% of them)
(2) The value of 100% achievement by humans may not reasonably be compared with 50% achievement in practical terms - if your car fails to start 50% of days you try,... (read more)