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.
Quasi-experimental research is research that will include features of a true experiment, but some elements may be missing. Three types of quasi-experimental research are: cross-sectional, longitudinal, and cross-sequential. Cross-sectional research studies make a comparison of different groups at the same time.