Answer:
observation
Step-by-step explanation:
When someone says "Sheila has a stain on her shirt," it is because a situation has occurred. This situation is exactly the fact that Sheila's shirt is stained and this can raise a series of assumptions of the reasons that created this stain. These assumptions are hypotheses, which will lead to investigations through experiments, which will yield results and will prove whether the assumptions about the stain on Sheila's shirt are real. This is an example of a scientific method.
Observation is the first stage of the scientific method and establishes a situation that was perceived, seen, but not interpreted.