EPI Challenge For You
An Authentic Science Research Experience for High School Students
Glossary of Terms
| Autonomy | The right of individuals to decide things for themselves – an ethical principle. |
| Association | A relationship between two factors. When two things turn up together. Tied, linked, connected. |
| Bias | Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of an exposure’s effect on the outcome. Information Bias - A systematic flaw in measuring an exposure or outcome that results in differences in quality of data between comparison groups. Recall Bias - A type of information bias that is due to systematic differences between groups in the accuracy and completeness of memory of past experiences. Selection Bias - Error due to systematic differences in characteristics between those who participate in a study and those who do not. |
| BRFSS | Behavioral Risk Factor Surveillance System. Uses health-related telephone surveys to assess risk factors among adults in the US. Run by the Centers for Disease Control and Prevention (CDC). BRFSS collects state data about U.S. residents regarding their health-related risk behaviors, chronic health conditions, and use of preventive services. BRFSS collects data in all 50 states as well as the District of Columbia and three U.S. territories. BRFSS completes more than 400,000 adult interviews each year, making it the largest continuously conducted health survey system in the world. |
| Case-Control Study | An observational study in which groups of people with and without an outcome are questioned about their past exposures. A comparison is made of how frequently the exposure is present among those with the outcome (cases) and those without the outcome (controls). |
| Cause | A factor that produces a change in another factor. |
| Cohort Study | An observational study of a defined population in which subsets can be identified as exposed, and not exposed to a factor of interest. The exposed and unexposed subsets are followed over a period of time, and comparisons are made between groups regarding the likelihood of having the health-related outcome under study. |
| Comparison Group | People who participate in a study and do not have the exposure of interest. People whose results are compared to the group that was exposed |
| Confounding | To confuse, to mistake for another, to mix together. A situation in which an association between an exposure and an outcome is observed as a result of the influence of a third (unobserved) factor called a confounder. The confounder is both associated with the observed exposure and is a cause of the outcome. Sometimes called a “lurking variable.” |
| Contingency Table | A cross-classification of data where categories of one variable are presented in rows and categories of another variable are presented in columns. The simplest contingency table is the 2x2 table. |
| Cross-Sectional Study | A study in which exposure and outcome are measured simultaneously in a given population or a sample of that population. This study can be thought of as providing a "snapshot" of the frequency of an exposure and outcome at a particular point in time. |
| Effect Modifier | The strength of an association between an exposure and an outcome is different depending on the level of the third variable. For example, the effect of exercise on heart disease is different in men than in women. |
| Enduring Understandings | The big ideas that reside at the heart of a discipline and have lasting value outside the classroom. |
| Enduring Epidemiological Understandings | The big ideas that reside at the heart of the science of epidemiology and have lasting value outside the classroom. These ideas include the following: Health and disease are not distributed haphazardly in a population. There are patterns to their occurrence. These patterns can be identified through the surveillance of populations. Examining these patterns of health and disease can help formulate hypotheses about their possible causes. A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed. When an exposure is hypothesized to have a detrimental effect, it is not ethical to intentionally expose a group of people. In these circumstances, studies can be designed that observe groups of free-living people with and without the exposure. One possible explanation for finding an association is that the exposure causes the outcome. Because studies are complicated by factors not controlled by the observer, other explanations also must be considered, including chance, bias, confounding, and reversed time order. |
| Epidemic | The occurrence of an outcome (health-related states or events) in a region clearly in excess of what is normally expected. |
| Epidemiology | The study of populations in order to determine the patterns and causes of health-related events and behaviors (collectively called "outcomes"). The ultimate purpose is to apply what's been learned to the prevention and control of health problems. |
| Ethics in Human Research | The right thing to do according to established principles of how to treat people well. In accordance with the accepted principles of right and wrong governing the conduct of a group. |
| Exposure | Something with which someone comes in contact. Something that impinges upon you. A catch-all term for agents, interventions, conditions, and policies. Many types of exposure can be studied in epidemiology. Among these are health-related behaviors and events; lifestyle or socioeconomic factors; chemical or physical exposures; psychological stress and others. |
| Generalizable | Extent to which what happened to a sample of a population who participated in a study is applicable to the population from which the sample was selected. |
| Habits of Mind | Characteristics of effective thinkers that are used when responding to challenges, the answer or solution to which is not immediately known. These habits include persisting; managing impulsivity; listening to others with understanding and empathy; thinking flexibly; creating, imagining and innovating; responding with wonderment and awe; applying past knowledge to new situations; striving for accuracy and precision; and questioning and posing problems. |
| Hypothesis | An educated guess about how things work. Most of the time a hypothesis in epidemiology can be written like this: "If [Exposure] ___, then [Outcome]____ will happen.“ Your hypothesis should be something that you can actually test, what's called a testable hypothesis. In other words, you need to be able to measure both exposure and outcome. |
| Inference | A conclusion reached on the basis of evidence and reasoning. |
| Informed Consent | An agreement that is given by a potential research participant following an explanation of all relevant information needed to make an informed decision about participating in a study. |
| Investigation | A study to find answers to questions. |
| Interpretation | An explanation for an observation. Tries to answer the question: “what does it mean?” |
| Natural Experiment | Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an outcome. |
| Observational Study | Epidemiological studies of natural experiments in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results. |
| Outcome | A result of an exposure. Many kinds of outcomes can be studied in epidemiology. Among these are a health-related behavior; infectious disease; chronic disease; trauma; injury and other temporary or permanent health conditions. |
| Pandemic | An epidemic that has spread to human populations across a wide geographic area, across multiple countries and continents, or even worldwide. |
| Prevalence | The number of people in the population or sample who experienced the outcome or effect, divided by the total number of people in the population or sample. Expressed as a fraction or a percentage. |
| Prevalence Ratio | A comparison of two prevalences. Calculated by dividing the prevalence of the outcome in the exposed by the prevalence of the outcome in the unexposed: a/(a+b) divided by c/(c+d). Prevalence Ratios (PR) indicate the following: - A PR of 1.0 indicates that prevalence in the exposed group is the same as prevalence in the unexposed group. |
| Public Health Surveillance | The planned and continuous collection of health-related data on populations. Needs to be communicated to those with a need to know. The information may lead to actions to control or precent a health problem. |
| Randomized Controlled Trial | An epidemiological experiment in which people are randomly assigned into groups to receive or not receive a treatment, vaccine, or other potentially beneficial intervention. Over time, the intervention and non-intervention groups are compared to see what proportions of each group have the desired beneficial outcome. |
| Representative | The extent to which a sample of people who are studied is generally the same as the population from which the sample was taken. |
| Research | Investigations designed to develop generalizable knowledge, that is, knowledge that has been created in such a way that what was learned about a study group can be applied to others who were not studied. |
| Response Rate | The number of completed survey instruments divided by the total number of persons who were given the opportunity to be surveyed. |
| Reversed Time Order | When the hypothesized time order of an exposure and an outcome is reversed, and the outcome actually comes before the exposure. |
| Scientific Literacy | The ability to understand scientific processes and to engage meaningfully with scientific information available in daily life. |
| Simulated Research | Research, often conducted for educational purposes, for which results will not be generalizable. |
| Statistical Significance | A term used in research to indicate confidence that a scientific finding is not due to chance. By convention, if there is only a 5% or lower chance that two things are together by coincidence (chance), the finding is generally considered statistically significant. Two important factors that influence calculations of statistical significance are the magnitude of the effect and the sample size. |
| Stratification | Process of separating a sample into subsamples (strata) according to specific criteria such as by age group, gender, or any other factor suspected to influence an association. Analysis by strata is a way of identifying confounders and effect modifiers. |
| Study Design | Procedures and methods, established beforehand, that are followed by the investigators conducting the study. |
| 2x2 Table | A tool used to express the number people with and without the exposure and with and without the outcome. A 2x2 table is the simplest contingency table. |
| Web of Causation | A diagram depicting the ways one or more exposures can lead to an outcome. |
| YRBSS | Youth Risk Behavior Surveillance System. The Youth Risk Behavior Survey (YRBS) provides data on health-risk behaviors among 9th-12th grade students in the United States, including behaviors that contribute to injuries and violence; alcohol or other drug use; tobacco use; sexual risk behaviors; unhealthy dietary behaviors; and physical inactivity. YRBS also measures the prevalence of obesity and asthma among youth and young adults. |