An investigation of human evaluation based on Post-editing and its relation with Direct Assessment has been carried out in the following paper:
"Machine Translation Human Evaluation: an investigation of evaluation based on Post-Editing and its relation with Direct Assessment" .
Luisa Bentivogli, Mauro Cettolo, Marcello Federico, Christian Federmann.
Proceedings of the 15th International Workshop on Spoken Language Translation (IWSLT 2018), Bruges, Belgium, 2018.
All data used in the analyses are available for download here.