In a study on mortality salience, one group of students with christian beliefs was made highly aware of their mortality by writing about what will happen to them when they die. in the control group, similar students completed a questionnaire that did not mention death. researchers found that

In this study, the researchers found that students in the mortality salience condition rated more favorably someone who validated their views than someone who did not. Mortality salience refers to the awareness of death to one's self.  In the study, students with Christian beliefs were made aware of the state of transience while others were not. 

The answer is "Self-report".

Explanation:

The self-report assessment includes a person or a group of individuals who share their opinions, convictions, and experiences employing inventories or surveys. Such calculations can be easily managed and considered more accurate than other evaluations. This information is usually collected in paper or electronic formats, or often in an interview.