The past simple

Referring to the procedures used in individual studies

The past simple form is common when academics refer to the procedures used in their own and others’ individual experiments and studies:

[reporting one’s own experiment/study]
In two studies, 65 three-year-olds, 57 five-year-olds, and 74 adults viewed video clips of animals or inanimate objects being transported by a person. For each clip, the child was asked whether the animal or object was moving.

[reporting experiments/studies by others]
Bogren et al (2000) statistically modelled the magnitude of such temperature deficits with respect to solar elevation.