U.S. National Library of Medicine

Introduction to Health Services Research : A Self-Study Course

Module 6: Basic Components of a Study (Page 3 of 11)

Essential Concepts

This page provides key concepts from this module. It is intended to be a synopsis of the content in the module.

Essential Concepts: Surveys

• Surveys gather data to describe the demographics of a group; the health status of a group of people at a particular time; the utilization of medical services; or the knowledge, beliefs, and attitudes of people regarding health practices.
• Surveys are a major data collection method in health services research.
• Survey research is extremely complex.
• Survey results often are difficult to interpret and generalize to other groups and time periods but provide wonderful insights into the practices and health conditions of large groups of people as well as clues for future investigation.

Essential Concepts: Cohort Studies

• Cohort studies observe groups of individuals before they develop a disease or a particular outcome.
• Cohort studies have the power to detect many different outcomes of an exposure and allow researchers to calculate a relative risk of developing a disease based on different exposures.
• It may take many years to detect changes in the groups.
• Because of the time involved and number of participants needed, cohort studies may be very costly.

Essential Concepts: Case-Control Studies

• case-control studies begin with the outcomes and do not follow people over time.
• researchers choose people with a particular result (the cases) and interview the groups or check their records to ascertain what different experiences they had. They compare the odds of having an experience with the outcome to the odds of having an experience without the outcome.

Essential Concepts: Randomized Clinical Trials (RCTs)

• RCTs follow two groups of people over time to see who achieves a particular result. In this case, the researchers assign or randomize the people to their groups.
• each person has an equal chance of being assigned to either group
• each group receives a different intervention. When the study period ends, the researchers evaluate their different outcomes and calculate the risk of one group developing the result compared to another.
• advantages include the advantage in assessing causality, and the intervention caused the results is clearly demonstrated.
• disadvantages include expense and time-consumption, and bias to the results if participants are not properly blinded.