In these situations, observational studies have value because they often suggest hypotheses that can be tested with randomized experiments or by collecting fresh data.
Dǎɣ idagan win,tiɣarawen ən akayad ilanat tamɣar falas hakabat agud iyan issənəhəjitan adobatnen atwirəm as iruman atiwajanen meɣ as assəməsədəw ən ijarawən aynaynen.