Vocab Flashcards
1
Q
Agent
A
A factor that is essential for a disease, chronic conditions, or injury to occur. Examples of agents include microorganisms, chemical substances, forms of radiation, and, in the case of injury, physical force. Agents can cause a health problem by either being introduced, being present in excess, or being present at deficient levels.
2
Q
Antibody
A
Any of a variety of proteins in the blood that are generated to produce immunity against microorganisms or their toxins.
3
Q
Association
A
The statistical relationship between two or more events, characteristics, or other variables.
4
Q
Attack rate
A
A form of incidence that measures frequency of disease, chronic conditions, or injury in a particular population for a limited time, such as during an outbreak. In calculating attack rates, the numerator is the number of new cases of a health problem during an outbreak, and the denominator is the population at the beginning of the period.
5
Q
Secondary Attack Rate
A
A measure of the frequency of new cases of a disease, chronic condition, or injury among the contacts of known case-patients.
6
Q
Bar chart
A
A visual display in which each category of a variable is represented by a bar. Bar charts are used to show variations in size among categories.
7
Q
Bias
A
A systematic deviation from the truth; any trend in the collection, analysis, interpretation, publication, or review of data that can lead to conclusions that are systematically different from the truth.
8
Q
Box plot
A
A visual display that summarizes data using a “box and whiskers” format to show the minimum and maximum values (ends of the whiskers), interquartile range (length of the box), and median (line through the box).
9
Q
Carrier
A
A person or animal who harbors the infectious agent for a disease and can transmit it to others, but does not show signs of the disease. A carrier may be asymptomatic (never show signs of the disease) or may show signs of the disease only during the incubation period, convalescence, or postconvalescence. The period of being a carrier may be short (a transient carrier) or long (a chronic carrier).
10
Q
Case
A
An instance of a particular disease, chronic condition, or type of injury. A variety of criteria may be used to identify cases (See Case definition), and the epidemiologic definition of a case is not necessarily the same as the ordinary clinical definition.
11
Q
Case-patient
A
A person in a case-control study who has the disease or health condition under investigation.
12
Q
Case definition
A
A set of standard criteria for determining whether a person has a particular disease or health condition. A case definition specifies clinical criteria and details of time, place, and person.
13
Q
Case-fatality rate
A
The proportion of people with a particular condition (case-patients) who die from that condition. In calculating case-fatality rates, the numerator is the number of people who die from the condition, and the denominator is the total number of people with the condition.
14
Q
Cause of disease
A
A factor (characteristic, behavior, event, etc.) that directly influences the occurrence of a disease. Reducing such a factor in a population should reduce occurrence of the disease.
15
Q
Census
A
The enumeration of an entire population, usually including details on residence, age, sex, occupation, ethnic group, marital status, birth history, and relationship to head of household.
16
Q
Chain of infection
A
A process that begins when an agent leaves its source through a portal of exit, is conveyed by some mode of transmission, and then enters through an appropriate portal of entry to infect a susceptible host.
17
Q
Class
A
A grouping of observations of values of a variable. Classes are created for convenience in analyzing frequency.
18
Q
Class boundaries
A
The values determining the upper and lower limits of a class
19
Q
Class interval
A
The span of values of a continuous variable that lies between the class boundaries.
20
Q
Clinical criteria
A
The symptoms and features of a disease that would be detected by physician analysis.
21
Q
Clinical disease
A
A disease that has been manifested by its symptoms and features
22
Q
Cluster
A
An aggregation of cases of a disease or other health condition that are closely grouped in time and place. The number of cases may or may not exceed the number expected, and frequently the expected number is not known. Cases of cancer and birth defects are often investigated as clusters.
23
Q
Cohort
A
A well-defined group of people who have had a common experience or exposure and are then followed up, as in a cohort study or prospective study, to determine the incidence of new diseases or health conditions.
24
Q
Birth Cohort
A
A group of people born during a particular period or year
25
Confidence interval
A range of values for a variable
26
Confidence level
The proportion of similarly constructed confidence intervals that include the parameter of interest
27
Confidence limits
The end points (i.e., the minimum and maximum values) of a confidence interval.
28
Contact
Exposure to a source of an infection; a person so exposed
29
Contagious
Capable of being transmitted from one person to another by contact or close proximity.
30
Contingency table
A table of cross-tabulated data that allows for calculating associations. The 2-by-2 table, with cases tabulated by exposure and outcome, is the contingency table most commonly used in epidemiology.
31
Control
The group of people without the health problem under study in a case-control study; a person in that group. For controls, investigators choose people who are as similar as possible to the cases, but without the health problem under study. In a case-control study, the control group is compared with the case group to determine associations between exposures and outcomes and to test hypotheses.
32
Cumulative frequency
In a frequency distribution, the number or proportion of cases with a particular value or less.
33
Cumulative frequency curve
A plot of the cumulative frequency rather than the actual frequency for each class interval of a variable. This type of graph is useful for identifying medians and quartiles and other percentiles.
34
Death-to-case ratio
The number of deaths attributed to a particular disease, chronic condition, or type of injury during a specified period divided by the number of new cases of that disease or injury identified during the same period.
35
Demographic information
The personal characteristics of age, sex, race, residence, and occupation. Demographic information is used in descriptive epidemiology to define the population at risk.
36
Denominator
The lower portion of a fraction. Epidemiologists use fractions to calculate rates, or ratios. The denominator is usually the population at risk, although it may also be a measure, such as person-time, that quantifies the population's exposure.
37
Determinant
Any factor that brings about change in a health condition or in other defined characteristics.
38
Distribution
The complete summary of the frequency and pattern of the values or categories of a measurement. In epidemiology, distribution is the frequency and pattern of health-related characteristics and events in a population.
39
Dot plot
A visual display of the specific data points of a variable
40
Droplet nuclei
The residue of dried droplets that is easily inhaled and exhaled and may remain suspended in air for long periods and be blown over great distances.
41
Droplet spread
The direct transmission of an infectious agent by means of the aerosols produced in sneezing, coughing, or talking.
42
Endemic health condition
A disease, chronic condition, or type of injury that is constantly present in a given geographic area or population group; may also refer to the usual prevalence of a disease or condition.
43
Environmental factor
An extrinsic factor, such as geology, climate, insects, sanitation, or health services, that affects an agent and the opportunity for exposure.
44
Epidemic
The occurrence of more cases of a particular type of disease, chronic condition, or injury than expected in a given area, or among a specific group of people, over a particular period of time.
45
Epidemic curve
A histogram that shows the course of an outbreak or epidemic by plotting the number of cases of a disease, chronic condition, or injury according to time of onset.
46
Epidemic period
The time span of an epidemic
47
Epidemiologic triad
The traditional model of infectious disease causation, which has three components: an external agent, a susceptible host , and an environment that brings the host and agent together so that disease occurs.
48
Epidemiology
The study of the distribution and determinants of health conditions or events in populations, and the application of this study to control health problems.
49
Analytic Epidemiology
The aspect of epidemiology concerned with why and how a health problem occurs. Analytic epidemiology uses comparison groups to provide baseline data so that associations between exposures outcomes can be quantified and hypotheses about the cause of the problem can be tested. Examples include cohort studies and case-control studies .
50
Applied Epidemiology
The application or practice of epidemiology to control and prevent health problems.
51
Descriptive Epidemiology
The aspect of epidemiology concerned with gathering, organizing, and summarizing data on "person" (Who is ill?), "time" (When did they become ill?), and "place" (Where could they have been exposed to the illness?). This information is then used to conduct analytic epidemiology.
52
Evaluation
Systematic and objective examination of activities to determine how relevant and effective they are.
53
Exposed group
A group whose members have had contact with a cause of, or possess a characteristic that is a determinant of, a particular health problem
54
Exposure
Coming into contact with a cause of, or possessing a characteristic that is a determinant of, a particular health problem.
55
Frequency
The amount, or number of occurrences, of a disease, chronic condition, injury, or other attribute or event in a population.
56
Frequency distribution
A complete summary of the frequencies of the values or categories of a variable. Frequency distribution is often displayed in a two-column table with the individual values or categories in the left column, and the number of observations in each category in the right column.
57
Frequency polygon
A graph of a frequency distribution in which values of the variable are plotted on the horizontal axis, and the number of observations are plotted on the vertical axis. Data points are plotted at the midpoints of the intervals and are connected with a straight line.
58
Graph
A visual display of quantitative data arranged on a system of coordinates
59
Health
A state of complete physical, mental, and social well-being and not merely the absence of disease or other infirmity.
60
Health indicator
Any of a variety of measures (e.g., mortality rate) that indicate the state of health of people in a defined population.
61
Health information system
A combination of health statistics from various sources. Data from these systems is used to learn about health status, health care, provision and use of services, and the impact of services and programs on health.
62
High-risk group
A group of people whose risk for a particular disease, health condition, or type of injury is higher than that of the rest of their community or population.
63
Histogram
A visual representation of the frequency distribution of a continuous variable. The class intervals of the variable are grouped on a linear scale on the horizontal axis, and the class frequencies are on the vertical axis. Rectangles are drawn so that their bases equal the class intervals, and their heights correspond to the class frequencies.
64
Host
A person or other living organism that is susceptible to an infectious agent under natural conditions
65
Host factor
An intrinsic factor (e.g., age, race, sex, behaviors) that influences an individual's exposure, susceptibility, or response to an agent.
66
Hyperendemic health problem
A disease, chronic condition, or type of injury that is constantly present at a high incidence and/or prevalence. Examples include diabetes among the Pima Indians in Arizona and Hepatitis B in China and elsewhere in Asia
67
Hypothesis
A supposition, arrived at from observation or reflection, that leads to refutable predictions; any conjecture cast in a form that will allow it to be tested and refuted
68
alternative hypothesis
The supposition that an exposure is associated with the health condition under study. The alternative is adopted if the null hypothesis proves implausible.
69
Null hypothesis
The supposition that an exposure is not associated with the health condition under study. The null hypothesis is the basis for most parametric tests for statistical significance.
70
Active immunity
Resistance developed in response to an antigen (infecting agentor vaccine) and usually characterized by the presence of antibody produced by the host.
71
Herd Immunity
The resistance of a group to an infectious agent. This group resistance exists because a high proportion of people in the group are immune to the agent. Herd immunity is based on the number of people who are susceptible and the probability that they will come into contact with an infected person. By vaccinating large numbers of people in a population to protect them from smallpox, health officials used herd immunity to control and eradicate the disease.
72
Passive immunity
Immunity conferred by an antibody produced in another host. This type of immunity can be acquired naturally by an infant from its mother or artificially by administration of an antibody-containing preparation (antiserum or immune globulin).
73
Incidence
A rate that measures the frequency with which a health problem, such as a new injury or case of illness, occurs in a population. In calculating incidence, the numerator is the number of new cases occurring in the population during a given period of time, and the denominator is the total population at risk during that time.
74
Incubation period
The period following exposure, when pathologic changes are not apparent, and ending with the onset of symptoms of an infectious disease.
75
Individual data
Data that have not been put into a frequency distribution
76
Infectivity
The proportion of people who are exposed to an agent and become infected
77
Interquartile range
The central portion of a distribution, calculated as the difference between the third quartile and the first quartile. This range includes the middle one-half of the observations in the set, leaving one-quarter of the observations on each side.
78
Latency period
The period following exposure, when pathologic changes are not apparent, and ending with the onset of symptoms of a chronic disease.
79
Arithmetic mean
The measure of central location commonly called the average. The arithmetic mean is calculated by adding all the values in a group of measurements and dividing by the number of values in the group.
80
Geometric mean
The mean, or average, of a set of data measured on a logarithmic scale
81
Measure of association
A quantified relationship between exposure and a particular health problem. Commonly used measures of association include relative risk, rate ratio, and odds ratio.
82
Measure of central location
A central value that best represents a distribution of data. Common measures of central location are the mean, median, and mode. Also called the measure of central tendency.
83
Measure of dispersion
A measure of the spread of a distribution out from its central value. Measures of dispersion used often in epidemiology are the interquartile range, variance, and the standard deviation.
84
Measurement scale
The complete range of possible values for a measurement. An example is the set of possible answers to a question in a survey.
85
Median
The middle value in a set of numbers (or the average of two middle numbers) above and below which lie an equal number of values. (See also Measure of central location)
86
Medical surveillance
Monitoring individuals who may have been exposed to a health problem, for the purpose of detecting early symptoms.
87
Midrange
The halfway point, or midpoint, in a set of observations. For most types of data, the midrange is calculated by adding the smallest observation and the largest observation and dividing by two. The midrange is usually calculated as an intermediate step in determining other measures.
88
Mode
The most frequently occurring value in a set of observations.
89
Morbidity
Disease; any departure, subjective or objective, from a state of physiological or psychological health and well-being.
90
Mortality rate
A measure of the frequency of occurrence of death in a defined population during a specified time interval.
91
Age-adjusted mortality rate
A mortality rate that has been statistically modified to account for the effect of different age distributions in different populations in a study.
92
Age-specific mortality rate
A mortality rate limited to a particular age group. In calculating age-specific mortality rates, the numerator is the number of deaths in the age group, and the denominator is the number of people in that age group.
93
Cause-specific mortality rate
The mortality rate from a specified cause. In calculating cause-specific mortality rates, the numerator is the number of deaths attributed to a specific cause during a specified time interval in a population, and the denominator is the size of the population at the midpoint of the time interval.
94
Crude mortality rate
A population's mortality rate from all causes of death.
95
Infant mortality rate
The mortality rate for children less than one year of age. In calculating infant mortality rates, the numerator is the number of deaths reported among this age group during a given time period, and the denominator is the number of live births reported during the same period. The infant mortality rate is usually expressed per 1,000 live births.
96
Neonatal mortality rate
The mortality rate for children from birth up to, but not including, 28 days of age. In calculating neonatal mortality rates, the numerator is the number of deaths in this age group during a given time period, and the denominator is the number of live births reported during the period. The neonatal mortality rate is usually expressed per 1,000 live births.
97
postneonatal mortality rate
The mortality rate for children from 28 days up to, but not including, 1 year of age. In calculating postneonatal mortality rates, the numerator is the number of deaths among this age group during a given time period, and the denominator is the number of lives births during the same period. The postneonatal mortality rate is usually expressed per 1,000 live births.
98
race-specific mortality rate
A mortality rate limited to a specified racial group. Both numerator and denominator are limited to that group.
99
sex specific mortality rate
A mortality rate among either males or females.
100
Natural history of disease
The course of a disease from the time it begins until it is resolved.
101
Necessary cause
A factor that must be present for a disease or other health problem to occur.
102
Nominal scale
A type of measurement scale. Nominal scales consist of qualitative categories whose values have no inherent order or rank. Information regarding the race, religion, and country of birth of people in a population is a good example.
103
Normal curve
A bell-shaped curve, which results when a normal distribution is graphed.
104
Normal distribution
The symmetrical clustering of values around a central location. A normal distribution 1) is a continuous, symmetrical distribution with both tails extending to infinity; 2) has an identical arithmetic mean, mode, and median; and 3) has a shape that is completely determined by the mean and standard deviation.
105
Notifiable disease
A disease that, by law, must be reported to public health authorities upon diagnosis.
106
Numerator
The upper portion of a fraction.
107
Observational study
An epidemiologic study in which there is no intervention and nature is allowed to take its course. Changes or differences in one characteristic are studied in relation to changes or differences in others.
108
Odds ratio.
A measure of association used in comparative studies to quantify the relationship between an exposure and a health outcome; also known as the cross-product ratio.
109
Ordinal scale
A type of measurement scale. Ordinal scales consist of qualitative categories whose values have a distinct order. The categories are qualitative in that there is no natural distance to be measured between their possible values. An example is social class (I, II, III).
110
Outbreak
Because the public sometimes perceives "outbreak" as less sensational than "epidemic," it is sometimes the preferred word. Sometimes the two words are sometimes differentiated, with "outbreak" referring to a localized health problem, and "epidemic," to one that takes in a more general area
111
Common source outbreak
An outbreak in which people are exposed to a common harmful influence, such as an infectious agent or toxin. The exposure period may be brief, or people may be exposed over a period of days, weeks, or longer, with the exposure being either intermittent or continuous.
112
point source outbreak
A common source outbreak in which the exposure period is relatively brief so that all cases occur within one incubation period.
113
propogated outbreak
An outbreak that does not have a common source, but instead spreads from person to person.
114
Outcome
Any or all of the possible results that may stem from exposure to a causal factor or from preventive or therapeutic interventions; all identified changes in health status that result from the handling of a health problem.
115
Pandemic
An epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population.
116
Pathogenicity
The proportion of people who are infected by an agent and then develop clinical disease.
117
Percentile
A set of cut points used to divide a distribution or a set of ranked data into 100 parts of equal area with each interval between the points containing 1/100 of the observations. For example, the 5th percentile is a cut point with 5% of the observations below it and the remaining 95% above it.
118
Person-time
The total of the units of time, whether weeks, months, or years, that people were exposed to a condition or were actively involved in a study. One person-year can represent a single person who was exposed for one year or an accumulation, such as two people who were each exposed for half a year.
119
Person-time rate
A measure of the incidence rate of an event (e.g., disease, injury, or death) in a population over an observed period. The person-time rate directly incorporates time into the denominator.
120
Pie chart
A circular chart depicting observed data and divided into "slices" that are proportional to the frequency of the categories of the variable assigned to them.
121
Population
The total number of inhabitants of a given area or country. In sampling, the population may refer to the units from which the sample is drawn, not necessarily the total population of people. A population can also be a particular group at risk, such as everyone who is engaged in a certain occupation.
122
Portal of entry
A pathway into the Portal of entry. A pathway into the host that gives an agent access to tissue that will allow it to multiply or act.
123
Portal of exit
A pathway by which an agent can leave its source.
124
Predictive value positive
A measure of the predictive value of a reported case or epidemic; the proportion of cases reported by a surveillance system or classified by a case definition that are true cases.
125
Prevalence
The number or proportion of cases or events or conditions in a given population.
126
Period prevalence
The amount of a particular disease, chronic condition, or type of injury present in a population over a period of time
127
Point prevalence
The amount of a particular disease, chronic condition, or type of injury present in a population at a single point in time.
128
Prevalence rate
The proportion of people in a population who have a particular disease, chronic condition, injury, or attribute at a specified point in time or over a specified period of time.
129
Proportion
A ratio in which the numerator is included in the denominator; the ratio of a part to the whole, expressed as a "decimal fraction"' (e.g., 0.2), a fraction (1/5), or a percentage (20%).
130
Attributable proportion
A measure of the impact of a causative factor on the public health; the proportion of a disease, chronic condition, or injury that can be attributed to exposure to a particular factor.
131
Proportionate mortality
The proportion of deaths in a population attributable to a particular cause over a period of time. Each cause of death is expressed as a percentage of all deaths, and the sum the proportionate mortality for all causes must equal 100%. These proportions are not mortality rates because the denominator is all deaths instead of the population in which the deaths occurred.
132
Public health surveillance
The systematic, ongoing collection, analysis, interpretation, and dissemination of health data. The purpose of public health surveillance is to gain knowledge of the patterns of disease, injury, and other health problems in a community so that we can work toward controlling and preventing them.
133
Range
In statistics, the difference between the largest and smallest values in a distribution; in common use, the span of values from smallest to largest.
134
Rate
An expression of the relative frequency with which an event occurs in a defined population.
135
Rate ratio
A comparison of two groups in terms of incidence rates, person-time rates, or mortality rates.
136
Ratio
The relative size of two quantities. A ratio is expressed by dividing one quantity by the other.
137
Relative risk.
A comparison of the risk of a health problem in two groups.
138
Reservoir
The habitat in which an infectious agent normally lives, grows, and multiplies. Humans, animals, and the environment can serve as reservoirs.
139
Risk
The probability that an individual will be affected by, or die from, an illness or injury within a stated time or age span.
140
Risk factor
An aspect of personal behavior or lifestyle, an environmental exposure, or a hereditary characteristic that is associated with an increase in the occurrence of a particular disease, chronic condition, or injury.
141
Risk ratio.
A comparison of the risk of a particular health problem in two groups.
142
Sample
A selected subset of a population. A sample may be random or nonrandom and representative or nonrepresentative.
143
Random sample
A sample of individuals chosen in such a way that each one has the same (and known) probability of being selected.
144
Representative sample
A sample whose characteristics correspond to those of the original or reference population.
145
Scatter diagram
A graphic display of the relationship between two variables. A dot is plotted on the graph for each set of paired values for two continuous variables, with one variable plotted on the horizontal axis, and the other plotted on the vertical axis.
146
Seasonality
Change in physiological status or in the occurrence of a disease, chronic condition, or type of injury that conforms to a regular seasonal pattern.
147
Sensitivity
The ability of a system to detect epidemics and other changes in the occurrence of health problems; the proportion of people with a health problem who are correctly identified by a screening test or case definition.
148
Sentinel event
A case of one of the notifiable diseases that has been included in a sentinel surveillance system.
149
Sentinel surveillance
A surveillance system using a prearranged sample of sources (e.g., physicians, hospitals, clinics) who have agreed to report all cases of one or more notifiable diseases.
150
Skewed
A distribution that is asymmetrical
151
Specificity
The proportion of people without a particular disease, chronic condition, or type of injury who are correctly identified by a screening test or case definition.
152
Sporadic illness
An illness that occurs infrequently and irregularly.
153
Spot map
A visual display of the geographic pattern of a health problem. On a map of the area, a marker is placed to indicated where each affected person lives, works, or may have been exposed. Spot maps can reveal clusters or patterns that provide clues to the identity and origins of the problem.
154
Standard deviation
A statistical summary of how dispersed the values of a variable are around its mean. Standard deviation is equal to the positive square root of the variance.
155
Standard error (of the mean)
The standard deviation of a theoretical distribution of sample means of a variable around the true population mean of that variable. Standard error is computed as the standard deviation of the variable divided by the square root of the sample size.
156
Statistical inference
Generalizations developed from sample data, usually with calculated degrees of uncertainty.
157
Statistical significance
The measure of how likely it is that a set of study results could have occurred by chance alone. Statistical significance is based on an estimate of the probability of the observed or a greater degree of association between independent and dependent variables occurring under the null hypothesis. The level of statistical significance is usually expressed by the P value.
158
Analytic Study
A study in which groups are compared to identify and quantify associations, test hypotheses, and identify causes. Two common types are cohort studies and case-control studies.
159
Case control study
An analytic study that compares a group of people with a certain disease, chronic condition, or type of injury (case-patients) with a group of people without the health problem (controls) to detect differences in characteristics such as exposure to an agent.
160
Cohort study
An observational analytic study in which enrollment is based on status of exposure to a certain factor or membership in a certain group. Populations are followed and disease, death, or other health-related outcomes are determined and compared.
161
Experimental study
A study in which investigators identify the type of exposure that each individual (clinical trial) or community (community trial) has had and then follows the individuals' or communities' health status to determine the effects of the exposure.
162
Sufficient cause
A causal factor or collection of factors whose presence is always followed by the occurrence of a particular health problem.
163
Survival curve
A curve that starts at 100% of the study population and shows the percentage of the population still surviving at successive times for as long as information is available. A survival curve may also be used to depict freedom from a health problem, complication, or some other endpoint.
164
Table shell
A table that is complete except for the data; the outline for a planned analysis
165
Transmission
Any mode or mechanism by which an infectious agent is spread to a susceptible host
166
Biologic transmission
Indirect transmission by a vector in which the infectious agent undergoes part of its life cycle inside the vector before it is transmitted to the host.
167
Direct transmission
Immediate transfer of an agent from a reservoir to a host by direct contact or droplet spread.
168
Indirect transmission
Transfer of an agent from a reservoir to a host either by being suspended in air particles (airborne), carried by an inanimate intermediary (vehicleborne), or carried by an animate intermediary (vectorborne).
169
Mechanical transmission
Indirect transmission by a vector in which the infectious agent does not undergo physiologic changes inside the vector.
170
Trend
Movement or change in frequency over time, usually upwards or downwards.
171
Secular trend
Changes over a long period of time, generally years or decades.
172
Clinical trial
An experimental study using data from individuals. Investigators identify the type of exposure that each individual has had and then follow the individuals' health status to determine the effects of the exposure.
173
randomized clinical trial
A clinical trial in which individuals are randomly assigned to exposure or treatment groups.
174
community trial
An experimental study that uses data from communities. Investigators identify the type of exposure that each community has had and then follow the communities' health status to determine the effects of the exposure.
175
randomized community trial
A community trial in which communities are randomly assigned to exposure or intervention groups.
176
Validity
The degree of accuracy of a measurement. For survey instruments, validity refers to what the questions actually measure in practice, as compared with what they are intended to measure.
177
Variable
Any characteristic or attribute that can be measured and can have different values.
178
Continuous variable
A variable that has the potential for having an infinite number of values along a continuum. Common examples are height and weight.
179
dependent variable
In a statistical analysis, a variable whose values are a function of other variable.
180
discrete variable
A variable that is limited to a finite number of values; data for such a variable. One example would be the number of cigarettes smoked per day by people in a study of smoking and lung cancer.
181
independent variable
An exposure, risk factor, or other characteristic being observed or measured that is hypothesized to influence an event or manifestation (the dependent variable).
182
Variance
A measure of the dispersion shown by a set of observations, defined by the sum of the squares of deviations from the mean , divided by the number of degrees of freedom in the set of observations
183
Vector
In epidemiology, an animate intermediary in the Vector. In epidemiology, an animate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host.
184
Vehicle
In epidemiology, an inanimate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host.
185
Virulence
The measure of severity of a disease, expressed as the proportion of people with the disease who become extremely ill or die.
186
Vital statistics
Systematically tabulated data on registered information about births, marriages, divorces, and deaths.
187
Years of potential life lost (YPLL)
A measure of the impact of premature death on a population. YPLL is calculated using a predetermined expected life span (usually 65 years) and is the sum of the differences between this age and the age at death for everyone who died early.
188
Zoonoses
An infectious disease that is transmissible from animals to humans
