Recording all instances of an event for a particular time period (such as how many times an older brother strikes his younger brother) without the subjects' awareness is an example of:

The answer is "naturalistic observation."

Naturalistic observation is an examination strategy ordinarily utilized by therapists and other social researchers. This procedure includes watching subjects in their regular habitat. This sort of research is frequently used in circumstances where leading lab inquire about is unreasonable, taken a toll restrictive or would unduly influence the subject's conduct.

Naturalistic observation varies from organized perception in that it includes taking a gander at a conduct as it happens in its regular setting without any endeavors at mediation with respect to the analyst.