All Terms Flashcards
The incidence of a disease in a population.
Absolute risk
The probability of making a type II error, i.e. the error of failing to reject a false null hypothesis.
Beta
The degree to which a measurement or an estimate based on measurements represents the true value of the attribute that is being measured.
Accuracy
The rate of outcome after controlling for a variable or variables across the entire population or both groups of comparison.
Adjusted Rates
Defined as the number of people at risk who develop a certain disease divided by the total number of people at risk.
Attack Rate
The amount or proportion of disease incidence that can be attributed to a specific exposure.
Attributable risk
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.
Bias
A form of selection bias that leads hospital cases and controls in a case-control study to be systematically different from one another.
Berkson’s bias
The probability of making a type I error, i.e. the error of rejecting a true null hypothesis.
Alpha
Keeping the observer(s) and/or subjects ignorant of the group to which the subjects are assigned.
Case
A distribution in which there are two peaks.
Bimodal Curce
A study in which cases are defined as those with the disease and controls are those without the disease. We can then study the significance between exposure and non-exposure from the two groups. Note: This study begins with diseased and non-diseased people.
Case-control study
An alternative to randomization in that no comparison is made with an untreated group or with a group receiving some other treatment.
Case study
Determines what percentage of people diagnosed as having a certain disease die within a certain time after diagnosis.
Case-fatality rate
Factors that increase risk for an event.
Causal Factors
A disease that will last for a considerable amount of time if not until death. Ill-effects and/or complications are usually delayed and gradual.
Chronic Disease
Disease characterized by signs and symptoms.
Clinical disease
A study that compares the incidence of disease between a group of exposed individuals and a group of non-exposed individuals. Note: This study begins with exposed and non-exposed people.
Cohort Study
Outbreak due to exposure of a group of persons to a noxious influence that is common to the individuals in the group.
common source epidemic
The computed interval with a given probability, e.g. 95%, that the true value of a variable is contained within the interval.
confidence interval
term used when variables or factors known to be related, or associated with, can influence the state of the subjects being studied.
confounding
Table of observed frequencies where the rows correspond to one variable of classification and the columns correspond to another variable of classification; simplest form is the two by two table.
contingency table
A study in which both exposure and disease outcome are determined simultaneously for each subject; it is as if we were viewing a snapshot of the population at a certain point of time.
cross-sectional study
The difference between a true value and that obtained as a result of faulty design of a study.
design bias
The process of determining health status and the factors responsible for producing it.
diagnosis
One determinant is directly associated with an outcome without any intermediate determinants.
direct cause
Transmitting an agent directly from the host to the susceptible. For example, person-to-person transmission by direct contact.
direct transmission
Study conducted during a foodborne-illness investigation where the investigators ask whether the suspect food was eaten or not eaten.
eaten/not eaten study
The change of one factor alters the outcome involved. Using a factor, i.e. age, to modify the effect of a putative causal factor under study.
effect modification
The habitual presence of a disease within a given geographic area. Also referred to as the usual occurrence of a given disease within such an area.
endemic
The incidence is calculated by using a period of time during which all of the individuals in the population are considered to be at risk for the outcome.
Cumulative incidence
The occurrence in a community or region of a group or illnesses of similar nature, clearly in excess of normal expectancy, and derived from a common or a propagated source.
Epidemic
The study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control health problems.
epidemiology
All that which is external to the individual human host.
encironment
A graphic plotting for the distribution of cases by times of onset.
epidemic curve
synonymous with attributable fraction.
etiologic fraction
The cause of a disease.
etiology
The absolute difference between the rates of disease in the entire population and the rates of disease among the non-exposed.
excess risk
The ability to generalize your treatment over an entire population based on the results of your sample study population.
external validity
People who have the disease and who are erroneously called “negative”
false negatives
People who do not have the disease and who are erroneously called “positive” by the test.
false positives
Number of people who ate a certain food and became ill divided by the total number of people who ate that food.
food specific attack rate
1) Introduction 2) Methods 3) Results 4) Discussion
four parts of scientific manuscript
A cohort study on cardiovascular disease, which was begun in 1948 in Massachusetts and consisted of a little over five thousand subjects.
Framingham study
Was the first to create vital statistics table.
Graunt John
A mathematical modeling technique that allows one to analyze prospectively collected data.
hazard model
Defined as the resistance of a group to an attack by a disease to which a large proportion of the members of the group are immune.
herd immunitiy
Father of medical statistics.
AB HILL
See retrospective cohort study.
historical cohort
Constant or uniform measures or variances across strata.
homogeneity
Denotes transmission from one person to another, directly or indirectly.
horizontal transmission
A person or other living animal that affords subsistence or lodgment to an infectious agent under natural conditions.
host
A study design which is a combination of more than one standard study design.
hybrid study design
A concept used that suggests that the visible or clinical cases of disease represent a small fraction of the actual prevalence.
iceberg concept of disease
Forcing in values for missing data.
imputation
The number of new cases of a disease that occur during a specified period of time among all person-time for a population at risk for developing the disease.
incidence denisty
The number of new cases of a disease that occur during a specified period of time among all persons in a population at risk for developing the disease. It is a measure of risk.
incidence rate
The interval from receipt of infection to the time of onset of clinical illness.
incubation period
The first case in a family or other defined group to come to the attention of the investigator.
index case
One determinant is indirectly associated with an outcome usually with intermediate determinants.
Indirect Cause
Transmission of an agent from host to susceptible by means of a vector, i.e. water.
Indirect transmission
An illness due to a specific infectious agent or its toxic products that arises through transmission of that agent or its products from an infected person, animal, or reservoir to a susceptible host, either directly or indirectly through an intermediate plant or animal host, vector, or the inanimate environment
infectious disease
A flaw in measuring exposure or outcome data that results in different quality of information between comparison groups.
information bias
Voluntary consent given by a subject for participation in a study after being informed of the purpose and risks.
informed consent
Interaction occurs when the incidence rate of disease in the presence of two or more risk factors differ from the incidence rate expected to result from their individual effects.
interaction
Systematic error due to interviewers’ subconscious or conscious gathering of selective data.
interviewer vias
Pioneered studies in vaccination. He was interested in predisposing people to cowpox as a means of controlling smallpox.
edward jenner
A measure of the degree of nonrandom agreement between observers of the same categorical variable.
kappa statistic
A list of postulates that should be met before a causative relationship can be accepted between a disease agent and the disease in question.
kochs postulates
An infection with no active multiplication of the agent , as when viral nucleic acid is incorporated into the nucleus of a cell as a provirus. Only the genetic message is present in the host, not the viable organism.
latent disease
Overestimation of survival time, due to the backward shift in the starting point for measuring survival that arises when diseases such as cancer are detected early, as by screening procedures.
lead time bias
A systematic error due to selection of disproportionate numbers of long-duration cases in one group but not in another.
length bias
A summarizing technique used to describe the pattern of mortality and survival in populations.
life table
Conducted one of the first randomized trials on scurvy by administering lemons randomly to the crew of a ship during the 18th century.
James Lind
A statistical analysis which determines an individual’s risk of the outcome as a function of a risk factor. The outcome of interest has two categories.
logistic regression
A study in which the exposure and non-exposure groups are ascertained. The groups are then followed up for several years into the future and incidence is measured.
longitudinal study
Study subject(s) who cannot or do not complete participation in a study for whatever reason.
loss to follow-up
An odds ratio that summarizes a number of odds ratios from a group of stratified contingency tables.
mantel-haenszel summary odds ratio
An analysis in which the study group and the control group are comparable with respect to extraneous factors.
matched analysis
Systematic error arising from inaccurate measurements of subjects on study variables.
measurement bias
The statistical analysis of a large collection of analyses resulting from individual studies for the purpose of integrating the findings.
meta-analysis
An obsolete theory, utilized prior to the 20th century, that stated disease being transmitted by a miasm, or cloud, that clung low on the surface of the earth.
miasmatic theory of disease
A type of bias that occurs when an individual is classified into the wrong category (ex. classifying an individual as a case when in actuality he/she is a control and vise versa).
misclassification bias
The way in which an infectious agent is transmitted (ex. airborne, direct contact, etc.).
mode of transmission
Any departure, subjective or objective, from a state of physiological or psychological well-being.
morbidity
Resulting in death.
mortality
Total number of deaths from a specified cause divided by the number of persons in the population at the midpoint of the specified time period. Any restrictions placed on the formula, such as an age range, apply to both the numerator and denominator. When restrictions are placed, we call it a specific rate. i.e. age-specific mortality rate.
mortality rate
A statistical analysis which uses more than one independent variable.
multivariate analysis
Each event or variable is independent from one another. No event or variable will have an effect on the probability of outcome for any other event or variable.
mutually exclusive
A hybrid study design in which a case-control study is nested in a cohort study.
nested case control study
Data which consists of names, labels, or categories.
nominal data
May include the following: preclinical disease, subclinical disease, persistent (chronic) disease, and latent disease.
nonclinical disease
An issue sometimes found during studies where patients either drop out of the study or may stop taking the agent assigned without admitting this to the researcher.
non-compliance
See retrospective cohort study
nonconcurrent prospective study
An infection that is obtained while a patient is in a hospital or as a result of being in a hospital (unrelated to the patient’s primary condition).
nosocomial infection
The statistical hypothesis that one variable has no association with another variable or that two or more population distributions do not differ from one another.
null hypothesis
Systematic difference between a true value and that actually observed, due to observer variation.
observer bias
The probability that the event will occur divided by the probability that the event will not occur.
odds
Odds ratio formula
OR=(a/b)/(c/d)=(ad)/(bc)
Data that may be arranged in order but the differences between data values either cannot be determined or are meaningless (ex. having a rating system of good, fair, or bad).
ordinal data
An epidemic limited to localized increase in the incidence of a disease, e.g., in a village or town.
outbreak
Research on outcomes of interventions usually used to describe the results of treatment in a clinical or surgical setting.
outcomes research
Extreme data values that may be correct but may disguise the true nature of the distribution when illustrated through a histogram.
outliers
When groups are matched too elaborately it can obscure evidence of a true causal association between variables.
overmatching
Refers to a worldwide epidemic.
pandemic
Immunity conferred by an antibody produced in another host and acquired naturally by an infant from its mother or artificially by administration of an antibody-containing preparation.
passive immunity
The postulated mechanisms by which the etiologic agent produces disease.
pathogenesis
A measure of how many individuals were affected by the disease during a specified time period.
period prevalence
An infection that persists for years and, sometimes, life.
Chronic disease
The sum of individual units of time that the persons in the study population have been exposed to the condition of interest.
person-time
Clinical pharmacologic studies of 20 to 80 patients that look at pharmacologic and toxic effects.
phase 1 study
Clinical investigations of 100 to 200 patients for effectiveness and relative safety.
phase 2 study
Large-scale randomized controlled trials for effectiveness and relative safety, which are often multi-centered.
phase 3 study
Postmarketing surveillance that is important for monitoring new agents as they come into general use by the public.
phase 4 study
An inert substance that looks, tastes, and smells like the active agent.
placebo
Prevalence of the disease at a point in time.
point prevalence
The proportion of patients who test positive that actually have the disease in question.
positive predictive value
- (the probability that you will make a type II error). The ability of a study to demonstrate an association if one exists.
power of a study
Disease that is not yet clinically apparent, but in a stage that is destined to progress to clinical disease.
pre-clinical disease
The quality of being sharply defined or stated, lack of random error.
precision
The number of affected persons present in the population at a specific time divided by the number of persons in the population at that time. Prevalence rates help to measure the burden of disease in a community.
prevalence rate
The person who introduces the disease into the family or group under study.
primary case
An action taken to prevent the development of a disease in a person who is well and does not have the disease in question.
primary prevention
Period in which signs and symptoms of a disease first appear.
prodromal period
A probable or likely projection of the course in which the disease will travel from the time of diagnosis to either the termination of the disease or death.
prognosis
Epidemic that progresses through a community or population; not from a single source.
propagated epidemic
Tendency of editors and authors to publish articles containing positive findings in contrast to reports that do not yield “significant” results.
publication bias
A method for sampling people in telephone surveys in which telephone numbers are randomly dialed.
random digit dialing
The unpredictability of the assignment of each subject.
randomization
A form of study design where a defined population is split into two groups: those that will receive the new treatment and those who will receive the current treatment. One will then compare the number of individuals who improved and who did not improve between the two groups.
randomized trails
A measure of the frequency of occurrence of a phenomenon.
rate
Value obtained by dividing one quantity by another; an expression of the relationship between a numerator and a denominator where the two usually are separate and distinct quantities.
ratio
Systematic error due to differences in accuracy or completeness of recall to memory of past events or experiences.
recall bias
The systematic error due to the inconsistent recruitment of subjects based on the identification of subjects by clinicians and other study subjects.
referral bias
The risk of disease in the exposed group divided by the risk of disease in the non-exposed group.
relative risk
The degree of stability exhibited when a measurement is repeated under identical conditions.
reliability
Selective revealing or suppression of information about past medical history.
reporting bias
Systematic error due to differences in characteristics between those that choose or volunteer to take part in a study and those who do not.
response bias
The number of completed or returned surveys divided by the total number of persons who would have been surveyed if all had participated.
response rate
A study at which an investigator will follow a cohort from some point in the past to a predetermined stopping point. The investigator can then compare the significance of who acquired the disease and who did not from the exposed and non-exposed groups.
retrospective cohort study
The probability that an event will occur (generally an unfavorable outcome).
risk
The process of determining risks to health attributable to environmental or other hazards.
risk assessment
Factors that increase a person’s risk for a disease.
risk factors
A selected subset of a population.
sample
Systematic error due to study of a nonrandom sample of a population.
sampling bias
Complete list of individual entities to be sampled from.
sampling frame
Individual entity that makes up the study sample.
sampling unit
The attack rate in susceptible people who have been exposed to a primary case.
secondary attack rate
The identification of people who have already developed a disease, at an early stage in the disease’s natural history, through screening and early intervention.
secondary prevention
The way in which cases and controls, or exposed and non-exposed individuals were selected in such a way that an apparent association is observed even if, in reality, exposure and disease are not associated. The apparent association is the result of selection bias.
selection bias
The ability of a test to identify correctly those who have the disease.
sensitivity
A condition that can be used to assess the stability or change in health levels of a population, usually by monitoring mortality statistics.
sentinel event
Visible indications that help to confirm the diagnosis of a disease or outcome, e.g., a rash
signs
Solved a historical epidemiological investigation of the cause of cholera in London, England. Attributed disease to contaminated water.
john snow
The ability of the test to identify correctly those who do not have the disease.
specificity
The observed number of deaths per year divided by the expected number of deaths per year.
standardized mortality ratios
Analyzing data where the sample is separated into several subsamples according to specified criteria such as age groups, socioeconomic status, etc.
stratified analysis
magnitude of the measure of association.
strength of effect
Disease that is not clinically apparent and not destined to become clinically apparent. Serologic response or culture of the organism often diagnoses it.
subclinical disease
Continuous analysis, interpretation, and feedback of systematically collected data.
surveillance
may occur when disease ascertainment is considerably better with a closely monitored population. This may lead to an erroneous estimate of the relative risk or odds ratio.
surveillance bias
a class of statistical procedures for analyzing data for studies that follow subjects over time.
survival analysis
Time from identification of an outcome to death.
survival time
The degree at which an individual is at risk for a certain disease or outcome. It is determined by a variety of factors including genetic background and nutritional and immunologic characteristics.
susceptiblity
Indicators, not necessarily visible, that help to confirm the diagnosis of a disease or an outcome, e.g., high blood pressure
symptoms
A situation in which the combined effect of two or more factors is greater than the sum of their solitary effects.
Synergistic effect
Tertiary prevention consists of limiting any disability by providing rehabilitation where disease, injury, or a disorder has already occurred and has already caused damage.
tertiary prevention
The amount of time from subject identification to the occurrence of the outcome.
time at risk
People without the disease that are correctly called “negative” by the test.
true negatives
People with the disease that are correctly called “positive” by the test.
truw positives
A type of contingency table; contains 2 columns and 2 rows where the rows correspond to one variable of classification and the columns correspond to another variable of classification.
2x2 table
Occurs when one concludes that treatments are different when in reality the treatments are not different.
type 1 error
A historical example (early 1900’s) of a woman who was a chronic carrier of Salmonella typhi. Over the course of her infection, she was responsible for at least 10 outbreaks in New York.
typhoid mary
The disease or injury which initiated the train of morbid events leading directly or indirectly to death or the circumstances of the accident or violence which produced the final injury.
underlying cause of death
A distribution in which there is but one peak.
unimodal curve
A statistical analysis which uses one independent variable.
univariate analyisis
The ability of a test to distinguish between who has a disease and who does not.
validity
In epidemiology, it is considered something that transports an infectious agent from an infected individual or it’s waste to a susceptible individual, it’s food, or immediate surroundings.
vector
Denotes transmission from one generation to another. Primarily genetic transmission.
vertical transmission
The degree of pathogenicity.
viruence
Certificates of birth, death, marriage, and divorce, required for legal and demographic purposes.
vital records
A systematic error attributed to differences in the reasons why people volunteer for a study.
volunteer bias
Current theory explaining causation.
web of causation
Recognizes that death occurring in the same person at a younger age clearly involves a greater loss of future productive years than were it to occur at an older age.
years of potential life lost
An infection or infectious disease transmissible under normal conditions from vertebrate animals to humans.
zoonosis
Occurs when one concludes that the treatments are not different when in reality the treatments are different.
Type 2 error
The subject to which an outcome is attributable, e.g., bacteria, virus, chemicals, etc.
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