The most common and obvious fossils are the preserved skeletal remains of animals. Other fossils, which are also evidence of past organisms, include leaf impressions, tracks and trails, burrows, droppings, and root casts.
Lesson Summary. Non-experimental research does not mean nonscientific. Non-experimental research means there is a predictor variable or group of subjects that cannot be manipulated by the experimenter. Typically, this means that other routes must be used to draw conclusions, such as correlation, survey or case study.
A quasi-experiment is an empirical study used to estimate the causal impact of an intervention on its target population without random assignment. Quasi-experimental research shares similarities with the traditional experimental design or randomized controlled trial, but it specifically lacks the element of random assignment to treatment or control.