This page provides definitions for common public health assessment concepts. It also serves as an index to additional resources on the NJSHAD system.

Index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Term	Definition

A

Age-Adjusted Rate	An age-adjusted rate is a rate that controls for age effects, allowing better comparability of rates across geographic areas. Age-adjustment may also be used to control for age effects when comparing across several years of data, as the age distribution of the population changes over time. [ more... ]
Age-Specific Rate	An age-specific rate is a rate in which both the numerator (number of events) and denominator (number in population at risk) are limited to a specific age group. It is calculated by dividing the total number of health events for the specific age group of interest by the total population in that age group. [ more... ]
Age-Specific Birth Rate	The number of resident births to females in a specific age group per 1,000 females in the age group.
Age-Specific Death Rate	The number of resident deaths in a specific age group per 100,000 population in the age group.
Apgar Score	A summary measure of an infant's clinical condition based on heart rate, respiratory effort, muscle tone, reflex irritability, and color taken at one and five minutes after delivery. Each of the factors is given a score of 0, 1, or 2; the sum of these five values is the Apgar score which can range from 0 to 10. A score of 10 is optimal and a low score (usually considered to be less than 7) is considered an indication of potential health problems and raises concerns about the subsequent health and survival of the infant.
Artifact	An artifact is any representation in data, such as observational or data entry errors, that would cause one to misinterpret the results.

B

Birth	A birth is the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of pregnancy, which, after such separation, breathes or shows any evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles. Births are sometimes referred to as live births. Birth data for New Jersey can be produced using the Custom Birth Query section of the NJSHAD Website.
Birth Defect	Birth defects include cleft lip/palate, club foot, spina bifida, Down syndrome, and other problems that happens while the baby is developing in the mother's body. Birth defects are also referred to as "congenital malformations, deformations, and chromosomal anomalies."
Birthweight	The first weight of the newborn obtained after delivery. Birthweight is recorded in grams.

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C

Cause of Death Classification	A system of specification of the diseases and/or injuries which led to death and the sequential order of their occurrence. The version of the system in use since 1999 is the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD- 10), sponsored by the World Health Organization.
Cause-Specific Death Rate	A cause-specific death rate is the number of resident deaths from a specific cause per 100,000 population. Cause-specific death rates can be crude or age-adjusted rates.
CI LL	Confidence interval lower limit.
CI UL	Confidence interval upper limit.
Confidence Interval	The confidence interval may be thought of as the range of probable true values for a statistic. In general, as a population or sample size increases, the confidence interval gets smaller. Estimates with smaller confidence intervals are referred to as more "precise." Less precise estimates, such as those calculated from small numbers, tend to have wide confidence intervals. Typically, the 95% confidence interval (calculated as 1.96 times the standard error of a statistic) indicates the range of values within which the statistic would fall 95% of the time if the researcher were to calculate the statistic (e.g., a percentage or rate) from an infinite number of samples of the same size drawn from the same base population. [ more... ]
Confounding Variable	A confounding variable is a variable that is related to, and may obscure one's view of, the variable of interest. For instance, when examining death rates across populations, the population's age distribution can be a confounding variable because higher death rates will be found in populations with a greater proportion of persons in older age groups. In such a case, one could use an age-adjusted rate to compare the populations.
Count	A count is the number of health events, such as a death or a reported disease incident, that occurred within a specified time period. [ more... ]
Crude Rates	A crude rate is a rate that has not been adjusted for artifacts or confounding variables, such as the age and sex composition of a population. [ more... ]
Crude Birth Rate	The number of resident births per 1,000 population (male and female).
Crude Death Rate	The number of resident deaths per 100,000 population.

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D

Delivery Weight	The first weight of the fetus obtained after delivery. Delivery weight is recorded in grams.
Disparity	Significant differences in the overall rate of disease incidence, prevalence, morbidity, mortality, or survival rates between one population and another. [ more... ]

E

F

Feeding at Discharge	The type of feedings (breast, formula, or both) given in the 24 hours prior to discharge from the hospital.
Fetal Death	A fetal death is death prior to the complete expulsion or extraction from its mother of a product of conception; the fetus shows no signs of life such as breathing or beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles. Fetal deaths are also referred to as stillbirths, miscarriages, or spontaneous abortions. New Jersey law requires the reporting of all fetal deaths of 20 or more weeks gestational age. An induced termination of pregnancy (ITOP) is a kind of fetal death, however ITOPs are reported separately from spontaneous fetal deaths. In New Jersey health data reports, fetal death refers only to spontaneous fetal deaths.
Fetal Mortality Rate	The number of resident fetal deaths of 20 or more weeks gestation per 1,000 resident live births plus fetal deaths of 20 or more weeks of gestation. (This rate is often referred to as Fetal Death Rate.)
First Birth Rate	Determined from the sum of number of births now living plus number of (live) births now dead stated on the birth certificate. If either of these is not stated, the sum is considered not stated. For those whose sum equals zero (i.e., first births), rates are computed per 1,000 female population.

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G

General Fertility Rate	The number of resident births per 1,000 females aged 15-44 years.
Gestational Age	The obstetric estimate of the length of time from the first day of the mother's last normal menstrual period to the date of delivery. See Measuring Gestational Age in Vital Statistics Data: Transitioning to the Obstetric Estimate for information about how it is calculated.

H

I

ICD Codes	ICD is the acronym for "International Classification of Diseases." It is a coding system maintained by the World Health Organization and the U.S. National Center for Health Statistics used to classify causes of death on death certificates and diagnoses, injury causes, and medical procedures for hospital and emergency department visits. These codes are updated every decade or so to account for advances in medical technology. Beginning in 1999, the U.S. changed over from the 9th revision (ICD-9) to the 10th revision (ICD-10) to record cause of death on death certificates.
Infant Death	An infant death is death within the first year of life. An infant must be live-born to be considered an infant death, otherwise it is a fetal death.
Infant Death Rate	The number of resident deaths under one year of age per 1,000 population. (The infant death rate is usually not reported by the New Jersey Department of Health and is often used interchangably with Infant Mortality Rate.)
Infant Mortality Rate (IMR)	The number of resident deaths under one year of age in a given year per 1,000 births in the same year.

J

K

Kotelchuck Index

A measure of adequacy of prenatal care. [ more... ]

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L

Leading Causes of Death	See "NCHS Leading Causes"
Life Expectancy	Average number of years of life remaining to a person at a particular age. [ more... ]
Low Birthweight (LBW)	Birthweight of less than 2,500 grams or approximately 5 pounds, 8 ounces.

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M

Marital Status	The marital status of the mother for statistical purposes is determined for data years after 1988 by the response to the birth certificate item, "Mother married? (At birth, conception, or any time between)".
Multiple Births	Individual births in twin, triplet, quadruplet, and higher order multiple deliveries.

N

NCHS Leading Causes	In order to provide a consistent ranking standard the National Center for Health Statistics (NCHS) prepared a list of 113 selected causes of death for use with ICD-10. The 33 major cause of death groups are taken from the list of 113. For more information about the NCHS rankings, see Cause of Death Ranking on the NCHS website. Leading causes of death for New Jersey can be calculated using the Custom Mortality Query section of the NJSHAD Website. [ more... ]
Neonatal Death	Death of an infant within the first 27 days of life.
Neonatal Mortality Rate	The number of resident infant deaths within the first 27 days of life per 1,000 live births.
Not Stated	An inclusive term used to represent data which are missing, unknown, not available, or not classifiable.

O

P

Parity	The number of previous live-born children a woman has delivered.
Percent Change	The difference between the new number, rate, or percentage and the old number, rate, or percentage divided by the old number, rate, or percentage multiplied by 100: (new - old)/old * 100
Perinatal Mortality	Definition I: The sum of fetal deaths occurring after 28 or more weeks of gestation plus infant deaths occurring less than seven days after live birth. Definition II: The sum of fetal deaths occurring after 20 or more weeks of gestation plus infant deaths occurring less than 28 days after live birth. Only spontaneous fetal deaths, not induced or intentional terminations of pregnancy, are included in this definition. (The age range used for perinatal mortality varies between reports and between organizations. Use care when comparing.)
Perinatal Mortality Rate	Definition I: The number of resident fetal deaths of 28 or more weeks gestation plus infant deaths occurring less than seven days after live birth per 1,000 resident live births plus fetal deaths of 28 or more weeks of gestation. Definition II: The number of resident fetal deaths of 20 or more weeks gestation plus infant deaths occurring less than 28 days after live birth per 1,000 resident live births plus fetal deaths of 20 or more weeks of gestation.
Plurality	Singleton, twin, triplet, quadruplet, etc.
Postneonatal Mortality	Death of an infant from 28 days to one year of life.
Postneonatal Mortality Rate	The number of resident infant deaths from 28 days to one year of life per 1,000 live births.
Primary Cesarean	Cesarean delivery of a woman who has never had a cesarean before.
Primary Cesarean Rate	The number of cesarean deliveries per 100 births to women who have not had a previous cesarean.

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Q

R

Rate	A rate is a fraction, in which the numerator is the number of people among whom an event occurred during a certain period of time, and the denominator is the total number of people in the population at risk for the same period of time. Rates are typically multiplied by some factor of ten so that the result is a whole number. [ more... ]
Repeat Cesarean	Cesarean delivery of a woman who has had one or more prior cesareans.
Repeat Cesarean Rate	The number of cesarean deliveries per 100 births to women who have had a previous cesarean.
Reliability	Reliability is a property of a measurement that refers to its precision, or the degree to which observations of identical phenomena yield identical results. In public health, we often use measures such as death rates or birth outcomes to indicate the true underlying risk of illness or disability in a population. Often such measures, when observed in small populations, are said to yield "unreliable results" because the observations tend to vary considerably over time. That fluctuation makes them an unreliable measure of the true underlying population risk. [ more... ]

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S

Small Numbers

"Small numbers" is a term that is used to denote a population or a survey sample that is relatively small, yielding imprecise estimates for the health event of interest. "Small" is defined differently for different purposes, but in general, populations that yield 20 or fewer health events in the specific time period are considered small. Even for complete count datasets, such as birth and death certificate datasets, random fluctuations over time will yield estimates that are not reliable. For instance, the death rate for a short time period from a small population will not reflect the true underlying death risk for that population. The precision of an estimate may be indicated by the confidence interval for the estimate. As the population size decreases, the confidence interval widens, indicating less precision, or less "confidence" with regard to how well the estimate reflects the true underlying risk in that population.

Statistic

A statistic is a number that summarizes data. A descriptive statistic summarizes data in a limited or bounded dataset. Examples include the average age of students in a class and the percentage of employees who purchased dependent health coverage. An inferential statistic summarizes data in a sample drawn from a larger population, of which the sample is intended to be representative. Statistics calculated from the sample are used to make inferences about the population, and are typically accompanied by a confidence interval, used to suggest the precision of the statistic. Examples include the percentage of youth in a survey who smoked cigarettes or the average body mass index among sampled persons.

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T

Teen Birth	Birth to a mother under 20 years of age.
Total Fertility Rate	Age-specific birth rates of women in five-year age groups multiplied by five and summed to form a total for all ages. This rate indicates the number of children a cohort of 1,000 women would bear if they experienced the existing age-specific birth rates throughout their childbearing years.
Trend	A trend is a view of multiple years of data so rate changes over time can be analyzed. A trend is often shown as a simple line graph so that the trend is easily visible. Due to the changing age distribution of the population (i.e., the "aging" of the population over time) it is useful to use age-adjusted rates to compare rates over several years.
Trimester of Pregnancy	The first trimester includes the first 12 weeks of pregnancy, the second trimester encompasses the thirteenth through twenty-fourth weeks and the third trimester is the period after the twenty-fourth week through delivery.

U

Underlying Cause of Death	The underlying cause of death is the disease or injury which initiated the chain of events leading directly to death or the circumstances of the unintentional injury or violence which produced the fatal injury. All cause-of-death data in NJSHAD relate to the underlying cause of death coded from the death certificate unless otherwise noted.
Unintentional Injury	Unintentional injuries include motor vehicle-related injuries, poisonings, falls, burns and smoke inhalation, drowning, suffocation, and other injuries. Unintentional injuries are commonly referred to as "accidents."

V

Vaginal Birth After Previous Cesarean (VBAC)	Vaginal delivery of a woman who has previously had a cesarean delivery.
Vaginal Birth After Previous Cesarean (VBAC) Rate	The number of vaginal births after previous cesarean (VBAC) deliveries per 100 births to women with a previous cesarean delivery.
Validity	Validity is a property of a measurement that refers to its accuracy, or the degree to which observations reflect the true value of a phenomenon. In public health, we are lucky because the validity of most of our measures is really quite good. "Cause of death" on death certificates is certified by a physician. Survey measures have been tested to maximize validity. Birthweight is measured and reported at the birth hospital. There are some measures that we question, for instance self-reported body weight, but on the whole, the measures we use have a high degree of validity. [ more... ]
Very Low Birthweight	Birth weight of less than 1,500 grams or approximately 3 pounds, 5 ounces.

W

Weighted Average

The weighted average, or weighted mean, is an average in which the data elements have been differentially weighted. Data elements with a high weight contribute more to the weighted average than do elements with a low weight. If all data components in the calculation have the same weight, it is called the arithmetic mean. In the case of age-adjusted rates for health events, a weighted mean is used to adjust, or age-standardize, health event rates for two or more populations with different age compositions.

X

Y

Years of Potential Life Lost (YPLL)

YPLL is a measure of the number of years not lived by each individual who died before reaching a predetermined age, usually 65 or 75. [ more... ]

Z

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