The ethical decision approach that requires persons to be guided by standards of equity, fairness and impartiality is the:

Postconventional Level

Explanation:

From a psychological viewpoint, the answer would be the postconventional level. There are three levels: preconventional, conventional, and postconventional.

Preconventional:

- Reasoning about a moral dilemma is based on self-interest, such as getting personal gains, making a good deal, and/or avoiding personal losses.  

Conventional:

- Reasoning about a moral dilemma is based on expectations, such as conforming to social norms to get approval from others and/or obeying legal rules.

Postconventional:

- Reasoning about a moral dilemma is based on "higher" principles, including people's individual rights in a society and/or abstract ideas about justice and equality.

Hope this helps! :)