She tested her hypothesis by injecting egalon into 100, one year old turtles. The turtles began laying eggs at an average of 20 months old. The researcher concluded that her hypothesis was right i.e. egalon is responsible for triggering egg production. It was concluded that wearing tight pants causes low sperm counts. You can't say anything about causation in this type of study.
Observational data are non-experimental data.
Such data are obtained without controlling the independent variables of interest. It was suspected that the amount of protein in a zebra fish diet affected the number of eggs laid at one time. 1000 zebra fish were divided into four groups. Group A received a protein free diet, group B received low levels of protein, Group C received medium levels and Group D received high levels. It was concluded that the amount of protein affects the number of eggs laid and specifically, high levels of protein cause high egg production and low levels of protein cause low egg production.