PS375 Chapter Notes - Chapter 3: Longitudinal Study
Document Summary
All research involves comparison, usually between different levels of an iv. If the iv is a nonmanipulable subject characteristic like age, researcher must select participants who already possess diff levels of the characteristic. Tests the same sample at least twice across some period of time. Usually used for naturally occuring rather than experimentally induced changes thus the use of delayed follow up tests in training/intervention research is not usually classified as longitudinal. Less common than cross sectional studies bc time consuming and expensive and more difficult to bring to successful completion. Any single longitudinal sample all born around same time consistutes a cohot/single generation and findings may be specific to this one generation. However longitudinal samples avoid campbell and stanley"s selection bias (selection of initially nonequivalent groups for comparison) because each participant is being compared with themself. Often dropout is not random but selective participants who are lost from the study are systematically different from those who remain.
