The passive voice is often used when describing methodology. Using the passive voice emphasizes the action taken rather than the entity performing the action. In each of the following examples, the author or authors are the (unspecified) actors.
The specimens were collected according to established protocols. (instead of “I collected specimens…”)
Several factors have been taken into consideration before categorizing artefacts. (instead of “I took several factors into consideration…”)
The questions for the interviews were formed using our theoretical framework. (instead of “We formed the questions…”)