Independence-Of-Irrelevant-alternatives criterion
if candidate X is the winner, then candidate X should still win even if another candidate is eliminated from the election
The independence of irrelevant alternatives (IIA) criterion is a principle of decision-making that states that the relative ranking of any two options should not be affected by the addition or removal of a third, irrelevant option. In other words, if we have a set of options and we add another option that is not chosen, the relative ranking of the original options should remain the same.
This criterion is important in fields such as economics, political science, and social choice theory. It is often used in the analysis of voting systems, where the presence or absence of a candidate who is unlikely to win should not affect the ultimate choice between the remaining candidates.
For example, in a simple two-candidate election, if a third candidate is introduced who has no realistic chance of winning, the choice between the two main candidates should not be affected. The relative ranking of the two candidates should remain the same, regardless of the presence or absence of the third candidate.
The IIA criterion is significant because it guarantees that the choice made by a group of decision-makers is consistent and stable. It helps to ensure that alternative options are evaluated independently and that the ultimate decision is based on the merits of each option. Without the IIA criterion, it would be possible for a less desirable option to be chosen simply because of the addition or removal of an irrelevant option.
In conclusion, the IIA criterion is a fundamental principle of decision-making that ensures the stability and consistency of decisions. It prevents irrelevant options from affecting the choice between valid options and enables decision-makers to make objective and unbiased choices.
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