HOSA / SciOly (Everything)

2 x 2 Table

A table of frequency or count data that involves 2 rows and 2 columns, used to show the relationship between disease and exposure, dividing persons into categories of diseased and exposed (a), diseased and not exposed (b), not diseased and exposed (c), and not diseased and not exposed (d).

2 x C Table

A table of frequency or count data that involves two rows and C columns of data.

5 Ws of Descriptive Epidemiology

Diagnosis or health event (what), Person (who), Place (where), Time (when), and Modes of Transmission (why/how).

A Case

Represents instances of the problem that one wants to study.

A-Cell

The number of exposed cases in a data layout that relates a dichotomous exposure variable to a dichotomous disease variable; the distribution of the random variable for the a-cell is used to derive the exact p-value for a test of hypothesis about a risk ratio, odds ratio, or rate ratio when the study sample size is small.

Acceptance Region

A set of possible values for the test statistic leading to the conclusion that the null hypothesis in a statistical test of hypothesis should not be rejected.

Accuracy

The degree to which a measurement is, on average, correct.

Acquired Immunity

Specific immunity that develops after exposure to a particular antigen, or after antibodies are transferred from one individual to another; types include natural and artificial, active and passive.

Active Immunity

Resistance developed in response to an antigen (such as an infecting agent or vaccine), usually characterized by the presence of antibody produced by the host.

Active Surveillance

Data actively collected for a specific purpose through direct outreach (e.g., interviews, surveys, record reviews); more accurate but resource-intensive compared to passive surveillance; relatively accurate reporting and detects local outbreaks, but is expensive and more difficult to develop / Public health surveillance in which the health agency solicits reports.

Active Transmission

The direct spread of a disease from an infected individual to a susceptible one.

Actual Parameter

A parameter that describes events under actual conditions; written as RRS = p1S/p0S where p1S and p0S denote the proportions who develop the disease from using substitutes for the two exposure groups.

Adjusted Effect Measure

A measure of effect (e.g., risk ratio, odds ratio, rate ratio) that is adjusted for one or more variables being controlled; the adjustment procedure is typically either a weighted average of stratum-specific estimates of effect or a measure determined from a mathematical model that accounts for control variables of interest.

Adjusted Estimate

An estimate of a measure of effect, such as an adjusted odds ratio, that controls for other variables.

Adjusted Exposure Odds Ratio (aEOR)

An odds ratio from a case-control study that adjusts for or controls for other variables.

Adjusted Odds Ratio (aOR)

An odds ratio that controls for other variables such as confounders.

Adjusted Prevalence Odds Ratio (aPOR)

An odds ratio obtained from a cross-sectional study that adjusts for or controls for other variables.

Adjusted Prevalence Ratio (aPR)

A prevalence ratio obtained from a cross-sectional study that controls for other variables.

Adjusted Rate Ratio (aIDR)

A rate ratio (incidence density ratio) that controls for other variables.

Adjusted Risk Ratio (aRR)

A risk ratio that controls for other variables.

Adult Mortality Rate

The probability that a person aged 15 will die before reaching the age of 60, expressed per 1,000 population.

Agar

A gelatinous substance that provides the proper nutritional environment to promote the growth of microorganisms.

Age- and Cause-Specific Mortality Rate

The number of deaths from a disease in one year from a specific age group divided by the number of persons of that age in the population at midyear.

Age-Adjusted Rates

Summary rates, risks, or prevalences for comparing different populations in which underlying differences in the age distribution are removed; also called age-standardized rates.

Age-Adjustment

A procedure used to calculate summary rates, risks, or prevalences for comparing different populations in which underlying differences in the age distributions are removed; also called age standardization.

Age-Specific Death Rates

Mortality rates calculated separately for defined age groups within a population, allowing for comparison of death risk across different ages.

Age-Specific Mortality Rate

The number of deaths from all causes in one year for a specific age group divided by the number of persons of that age in the population at midyear.

Age-Standardized Death Rates

Death rates that have been statistically adjusted to account for differences in age distribution across populations, enabling valid comparisons between groups or over time.

Agent

An infectious microorganism or parasite, chemical substance, or physical force whose presence, excessive presence, or relative absence is essential for the occurrence of a disease or injury; the first component of the chain of infection.

Agent Factors

Biological (bacteria, etc.), chemical (poison, alcohol, smoke), physical (auto, radiation, fire), and nutritional (lack of or excess of).

Airborne Transmission

The agent is carried from the source to the host suspended in air particles / Pathogen travels through air; occurs when infectious agents are carried by dust or droplet nuclei suspended in air; considered a type of indirect transmission.

All-Causes Mortality

A risk or rate measure of the incidence of dying from all causes.

Alternative Hypothesis

The supposition that an exposure is associated with the health condition under study, adopted if the null hypothesis proves implausible / A statistical hypothesis that disagrees with the null hypothesis and typically indicates what the investigator is interested in detecting; can be one-sided or two-sided.

Amantadine

An antiviral drug sometimes used to prevent or moderate influenza among those at high risk of severe illness from the disease.

Analytic Studies

A study with the purpose of identifying and quantifying the relationship between an exposure and an outcome and testing hypotheses about causal relationships by comparing case-patients and those in an appropriate comparison group.

Analytical Epidemiology

A form of epidemiology that investigates causes and associations between factors or events and health; aims to research risk and protective factors of diseases, providing the why and how disease and other health events spread or occur / A type of epidemiology concerned with the search for causes and effects, used to quantify the association between exposures and outcomes and to test hypotheses about causal relationships.

Analytical Study

An epidemiological study designed to test hypotheses about the relationship between exposures and health outcomes by examining associations between variables.

Antibiotic

A medicine that limits the growth of or destroys microorganisms.

Antibody

A blood protein produced in response to and counteracting a specific antigen.

Antigen

Any substance (such as a toxin or the surface of a microorganism or transplanted organ) recognized as foreign by the human body that stimulates the production of antibodies.

Antimicrobials

Anything that inhibits the growth of microbes.

Anthrax

An infectious disease caused by the bacterium Bacillus anthracis, which can affect the skin, lungs, or gastrointestinal tract and is notable in epidemiology as a potential agent of bioterrorism.

Application to Prevention and Control

The aims of public health — to promote, protect, and restore health.

Applied Epidemiology

The application or practice of epidemiology to control and prevent health problems.

Apriori Criteria

Criteria that must be assessed prior to considering the actual data in one's study.

Arbovirus

Any of a group of viruses that are transmitted between hosts by mosquitoes, ticks, and other arthropods.

Arenavirus

A type of RNA virus, known as the cause of Lassa fever.

Arithmetic Mean

The measure of central location, commonly called the average, calculated by adding all the values in a group of measurements and dividing by the number of values in the group.

Arithmetic-Scale Line Graph

A graph that displays patterns or trends by plotting the frequency (e.g., number, proportion, or rate) of a characteristic or event during some variable, usually time, with the y-axis using an arithmetic scale.

Arthropod

An organism that has jointed appendages and segmented external skeleton (e.g., flies, mosquitoes, ticks, or mites).

Aseptic Technique

The use of practices and procedures to prevent contamination from pathogens.

Aspirin Benefits

The evidence-based findings that regular low-dose aspirin use can reduce the risk of cardiovascular events such as heart attacks and strokes in certain high-risk populations.

Association

A relationship between two characteristics such that they change predictably together / The relationship between two or more variables; in epidemiology, an association is quantified using a measure of effect such as an odds ratio or risk ratio.

Asymmetrical

A type of distribution where the shape to the right and left of the central location is not the same; often referred to as a skewed distribution; the mean, median, and mode of an asymmetrical distribution are not the same.

Asymptomatic

Without symptoms.

At Risk Population

The group of individuals who are susceptible to developing a particular disease or condition and are therefore included in the denominator when calculating disease rates.

Attack Rate

The proportion of people exposed to a source of infection who subsequently develop the disease, commonly used during outbreak investigations / The rate at which a group experienced an outcome or illness over a short period of time, equal to the number sick divided by the total number in that group; incidence proportion.

Attribute

A risk factor that is an intrinsic characteristic of the individual person, animal, plant, or other type of organism under study (e.g., genetic susceptibility, age, sex).

Attributable Fraction (AF)

The proportion of disease in the population that can be attributed to a particular exposure; also called etiological fraction or population attributable fraction / Formula: [(incidence in P) − (incidence in unexposed)] / (incidence in P).

Attributable Fraction (Exposed)

The proportion of disease cases among exposed individuals that can be attributed to the exposure itself, assuming a causal relationship.

Attributable Prevalence

Synonym for prevalence difference.

Attributable Proportion

A measure of the public health impact of a causative factor; the proportion of a health state or event among exposed persons that can be attributed to the exposure.

Attributable Rate

Synonym for rate difference.

Attributable Risk (AR)

The difference in the rate of a condition between an exposed group and an unexposed group, representing the excess risk due to the exposure / Formula: (incidence in exposed group) − (incidence in unexposed group).

Attributable Risk Percent Among Exposed

The proportion or corresponding percentage of exposed cases attributable to exposure; EFe = I/I1, where I1 is the number of exposed cases that actually occurred and I denotes the excess number of exposed cases due to exposure.

Average Duration of Disease

The mean length of time a disease persists in affected individuals, which influences the prevalence of the disease in a population.

Average Rate

Number of new cases in a time interval divided by the total amount of disease-free person-time accumulated during that interval.

Away from the Null

Direction of bias in which the target parameter is over-estimated, i.e., the biased estimate is further away from the null value than is the correct estimate.

Axis

One of the dimensions of a graph; in a rectangular graph, the x-axis is the horizontal axis and the y-axis is the vertical axis.

Back-Door Path

A path in a causal diagram (DAG) in which two variables have a common cause, representing a non-causal association between them.

Backwards

The directionality of a study in which the health outcome is observed before the exposure variable is observed; the study proceeds backwards over time; a case-control study always has backwards directionality.

Bacteria

Unicellular prokaryotes that have no organized internal membranous structures such as nuclei, mitochondria, or lysosomes; rod-shaped, spherical, and helical rods are the three most common shapes; do not rely on a host to reproduce and are treatable with antibiotics.

Bactericide

An agent that kills bacteria.

Balanced Tables

Two-way tables with cell frequencies all about the same size.

Bangkok Charter for Health Promotion

A 2005 WHO document that extended the principles of the Ottawa Charter by addressing the actions needed to achieve health in a globalized world, emphasizing policies, partnerships, and advocacy.

Bar Charts

Graphical displays that use rectangular bars of varying heights or lengths to represent and compare the frequency or magnitude of categorical data.

Bar Chart, 100% Component

A stacked bar chart in which all bars or columns are the same length, and the measured axis represents 0%-100%.

Bar Chart, Deviation

A bar chart displaying either positive or negative differences from a baseline.

Bar Chart, Grouped

A bar chart displaying quantities of two variables, represented by adjoining bars or columns of categories of one variable, separated by space between groups.

Bar Chart, Stacked

A bar chart displaying quantities of two variables, represented by subdivided bars or columns separated by space between bars or columns.

Bayes' Theorem

A mathematical theorem about conditional probabilities showing how the probability of a condition given a test result can be deduced from the probability of that test result given the condition; used to show that EOR equals ROR under certain conditions and to express predictive value in terms of sensitivity, specificity, and prevalence parameters.

Berkson's Bias

A type of bias in case-control studies involving hospital patients as cases and/or controls; results because persons with two disease conditions or high-risk behaviors are more likely to be hospitalized than subjects with a single condition.

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 risk of disease; in epidemiology, does not imply intentional deviation.

Bias, Information

Systematic difference in the collection of data regarding the participants in a study (e.g., about exposures in a case-control study, or about health outcomes in a cohort study) that leads to an incorrect result or inference.

Bias, Selection

Systematic difference in the enrollment of participants in a study that leads to an incorrect result or inference.

Binary

A variable that takes on one of two possible values, usually coded as 0 or 1.

Bimodal

Having two data peaks.

Binomial

A variable that has the binomial distribution, i.e., the distribution of a random variable whose values represent the number of successes in n trials, with a certain fixed probability of success (p); often denoted as B(n,p).

Binomial Distribution

The distribution of a random variable whose values represent the number of successes in n trials, with a certain fixed probability of success (p); often denoted as B(n,p).

Biological Monitoring

The measurement of a substance or its metabolites in biological samples such as blood or urine to assess an individual's internal exposure to environmental or occupational agents.

Biological Plausibility

A criterion for establishing causation in epidemiology, requiring that the observed association between an exposure and a disease be consistent with existing biological and medical knowledge.

Biological Vector

A biting insect that transmits disease / Indirect transmission by vector in which the infectious agent undergoes biologic changes inside the vector as part of its life cycle before it is transmitted to the host.

Biostatistics

The analysis of data and its application to health care; includes jobs such as Biostatistician, Medical and Health Services Manager, and Health Informatics Specialist.

Birth Cohort

A group of persons born during a particular period or year.

Birth Rate, Crude

The number of live births during a specified period divided by the mid-period population, usually expressed per 1,000 population.

Blinding

A feature of a clinical trial in which the patient or subject and/or the investigator is unaware of the treatment assigned.

Blood Pressure

The pressure exerted by the blood against the walls of blood vessels.

Body Temperature

A measurement of the degree of heat of the deep tissues of the human body.

Bovine Spongiform Encephalopathy (BSE)

A fatal, progressive neurological disorder affecting cattle, caused by abnormal prion proteins; linked to variant Creutzfeldt-Jakob disease (vCJD) in humans through consumption of contaminated beef products.

Box Plot

A visual display that summarizes data by using a "box and whiskers" format to indicate the minimum and maximum values (ends of the whiskers), interquartile range (length of the box), and median (line through the box).