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Glossary of terms used in health research - N

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  • N of 1 randomized trial
    • A randomized trial in an individual to determine the optimum treatment for that individual. The individual is given repeated administrations of experimental and control interventions (or of two or more experimental treatments), with the order of the treatments being randomized.
  • Narration
    • MeSH
      The act, process, or an instance of narrating, i.e., telling a story. In the context of medicine or ethics, narration includes relating the particular and the personal in the life story of an individual.
  • Narrative data
    • Verbal answers that take the form of a story or explanation, or which describe a series of events.
  • Narrative review
    • A review article (e.g., a typical book chapter) that is not conducted using methods to minimize bias (in contrast to a systematic review).
      Narrative review is sometimes used to describe a non-systematic review.
  • Narrative systematic review
    • Systematic review of heterogeneous studies, where it is more appropriate to describe the range of available evidence than to combine the findings into an overall result. A narrative systematic review can be conducted on both quantitative and qualitative research.
  • Natality
    • Births as a component of population change.
  • National health programs
    • MeSH
      Components of a national health care system which administer specific services, e.g., national health insurance.
  • Natural history
    • MeSH - Wikipedia
      As distinct from prognosis, natural history refers to the possible consequences and outcomes of a disease or condition and the frequency with which they can be expected to occur when the disease condition is untreated.
      A former branch of knowledge embracing the study, description, and classification of natural objects (as animals, plants, and minerals) and thus including the modern sciences of zoology, botany, and mineralogy insofar as they existed at that time. In the 17th, 18th, and 19th centuries it was much used for the generalized pursuit of certain areas of science.
  • Natural history of disease
    • Wikipedia
      The temporal course of disease from onset (inception) to resolution.
  • Natural history study
    • Wikipedia
      A study that follows a group of people over time who have, or are at risk of developing, a specific medical condition or disease. A natural history study collects health information in order to understand how the medical condition or disease develops and how to treat it.
      Study of the natural development of something (such as an organism or a disease) over a period of time.
  • Necessary cause
    • A causal factor whose presence is required for the occurrence of the effect (of disease).
  • Needs assessment
    • MeSH - Wikipedia
      A systematic procedure for determining the nature and extent of health needs in a population, the causes and contributing factors to those needs and the human, organizational and community resources which are available to respond to these.
      Needs assessment (or needs analysis) is the systematic appraisal of a perceived phenomenon as well as the appropriateness of the proposed intervention.
      Systematic identification of a population's needs or the assessment of individuals to determine the proper level of services needed.
  • Negative correlation
    • A negative correlation between two variables implies that as one variable gets bigger the value of the other variable becomes smaller.
  • Negative effect
    • As clinical studies accumulate, it is more common for effects to shrink than to increase. Negative effects are smaller or less dramatic than effects from previous studies.
  • Negative likelihood ratio
    • Wikipedia
      The ratio of the probability that an individual with the target condition has a negative test result to the probability that an individual without the target condition has a negative test result. This is the same as the ratio (1-sensitivity/specificity).
  • Negative predictive value
    • Wikipedia
      In screening/diagnostic tests: a measure of the usefulness of a screening/diagnostic test. It is the proportion of those with a negative test result who do not have the disease, and can be interpreted as the probability that a negative test result is correct. It is calculated as follows: NPV = Number with a negative test who do not have disease/Number with a negative test.
  • Negative study
    • A term often used to refer to a study with results that either do not indicate a beneficial effect of treatment or that have not reached statistical significance. The term can generate confusion because it can refer to either statistical significance or the direction of effect. Studies often have multiple outcomes, the criteria for classifying studies as ‘negative’ are not always clear and, in the case of studies of risk or undesirable effects, ‘negative’ studies are ones that do not show a harmful effect.
  • Neonatal intensive care
    • MeSH
      Continuous care and monitoring of newborn infants with life-threatening conditions, in any setting.
  • Neonatal intensive care unit
    • MeSH - Wikipedia
      A neonatal intensive care unit, usually shortened NICU and also called a newborn intensive care unit, intensive care nursery (ICN), and special care baby unit (SCBU), or a humidicrib, is a unit of a hospital specializing in the care of ill or premature newborn infants.
      Hospital units providing continuing surveillance and care to acutely ill newborn infants.
  • Neonatal mortality
    • Wikipedia
      Death of a liveborn infant within the first 28 days.
  • Neonatal mortality rate
    • Wikipedia
      Number of deaths during the first 28 completed days of life per 1,000 live births in a given year or other period. Neonatal deaths (deaths among live births during the first 28 completed days of life) may be subdivided into early neonatal deaths, occurring during the first 7 days of life, and late neonatal deaths, occurring after the 7th day but before the 28th completed day of life.
      The number of deaths to infants under 28 days of age in a given year per 1,000 live births in that year.
  • Neonatal period
    • The neonatal period commences at birth and ends 28 completed days after birth.
  • Neonatal screening
    • MeSH
      The identification of selected parameters in newborn infants by various tests, examinations, or other procedures. Screening may be performed by clinical or laboratory measures. A screening test is designed to sort out healthy neonates from those not well, but the screening test is not intended as a diagnostic device, rather instead as epidemiologic.
  • Net primary school enrolment rate
    • Enrolment of the official age group for primary level education expressed as a percentage of the corresponding population.
  • Net reproduction rate
    • Wikipedia
      The average number of daughters that would be born to a woman (or a group of women) if she passed through her lifetime conforming to the age-specific fertility and mortality rates of a given year. This rate is similar to the gross reproduction rate but takes into account that some women will die before completing their childbearing years. An NRR of one means that each generation of mothers is having exactly enough daughters to replace itself in the population. See also total fertility rate and replacement-level fertility.
  • Neural network
    • Wikipedia
      The application of nonlinear statistics to pattern-recognition problems. Neural networks can be used to develop clinical prediction rules. The technique identifies those predictors most strongly associated with the outcome of interest that belong in a clinical prediction rule and those that can be omitted from the rule without loss of predictive power.
  • New drug application
    • Wikipedia
      An application submitted by the manufacturer of a drug to the FDA - after clinical trials have been completed - for a license to market the drug for a specified indication.
  • News
    • News [MeSH - publication type]: works consisting of an announcement or statement of recent or current events of new data and matters of interest in the field of medicine or science. In some publications, such as "Nature" or "Science," the news reports are substantively written and herald medical and scientific data of vital or controversial importance.
  • Nominal categorical data
    • Data in which the categories cannot be ordered one above another. Examples of categorical nominal variables are sex and marital status.
  • Nominal scale
    • Classification into unordered qualitative categories; e.g., race, religion, and country of birth as measurements of individual attributes are purely nominal scales, as there is no inherent order to their categories.
  • Nominal variable
    • A variable that can be classified into a category (e.g., male or female sex); often called categorical variable. A categorical variable may be nominal or ordinal. Categorical variables can be defined according to attributes without any associated order (e.g., medical admission, elective surgery, or emergency surgery); these are called nominal variables. A categorical variable can also be defined according to attributes that are ordered (e.g., height such as high, medium, or low); these are called ordinal variables.
  • Nomogram
    • MeSH - Wikipedia
      Graphic scale facilitating calculation of a probability. The most-used nomogram in the evidence-based medicine world is one developed by Fagan to move from a pretest probability, through a likelihood ratio, to a posttest probability.
      Graphical representation of a statistical model containing scales for calculating the prognostic weight of a value for each individual variable. Nomograms are instruments that can be used to predict outcomes using specific clinical parameters. They use algorithms that incorporate several variables to calculate the predicted probability that a patient will achieve a particular clinical endpoint.
  • Nonadherent
    • Patients are nonadherent if they are not exposed to the full course of a study intervention (e.g., most commonly, they do not take the prescribed dose or duration of a drug or they do not participate fully in the study program).
  • Nonblinded
    • Describes a clinical trial or other experiment in which the researchers know what treatments are being given to each study subject or experimental group. If human subjects are involved, they know what treatments they are receiving.
  • Nonclinical study
    • Biomedical studies not performed on human subjects.
  • Nonconsecutive case series
    • Wikipedia
      A clinical study that includes some, but not all, of the eligible patients identified by the researchers during the study registration period. This type of study does not usually have a control group.
  • Non-inferiority trial
    • A trial with the primary objective of showing that the response to the investigational product is not clinically inferior to a comparative agent (active or placebo control).
      A trial designed to determine whether the effect of a new treatment is not worse than a standard treatment by more than a pre-specified amount. A one-sided version of an equivalence trial.
  • Non-interactive programs
    • Programs that use didactic methods (i.e. lecturers, presentation of films).
  • Non-maleficence
    • An ethical principle implying that where research involves experimentation on human subjects, the subjects should suffer no harm.
      Literally, not causing harm. A prima facie principle in bioethics, sometimes subsumed under the principle of beneficence. An obligation traditionally at the heart of medical ethics—the “first do no harm” component of the Hippocratic Oath—non-maleficence can be seen as distinct from the obligation to produce good.
  • Non-nominal linked information
    • Information linked to the person by a code (not including personal identification) known to the investigator.
  • Nonparametric statistics
    • MeSH - Wikipedia
      A class of statistical methods applicable to a large set of probability distributions used to test for correlation, location, independence, etc. In most nonparametric statistical tests, the original scores or observations are replaced by another variable containing less information. An important class of nonparametric tests employs the ordinal properties of the data. Another class of tests uses information about whether an observation is above or below some fixed value such as the median, and a third class is based on the frequency of the occurrence of runs in the data.
  • Nonprobability sampling
    • Wikipedia
      A non probability sample is one in which individuals are selected for a survey on the basis of some shared characteristic. For example, all the students in the same classroom, or all the patients attending a diabetes clinic. These examples, also known as convenience samples, introduce a bias into the measurement of the outcome of interest. For example, patients who attend a diabetes clinic may either already know or suspect that they suffer from the disease. Thus, the prevalence of diabetes in this sample is likely to be very high, and not representative of the prevalence of diabetes in the community.
  • Nonrandomized clinical trial
    • A clinical trial in which the participants are not assigned by chance to different treatment groups. Participants may choose which group they want to be in, or they may be assigned to the groups by the researchers.
  • Nonrandomized study
    • Any quantitative study estimating the effectiveness of an intervention (harm or benefit) that does not use randomization to allocate units to comparison groups (including studies where ‘allocation’ occurs in the course of usual treatment decisions or peoples’ choices, i.e. studies usually called ‘observational’). To avoid ambiguity, the term should be substantiated using a description of the type of question being addressed. For example, a 'non-randomized intervention study' is typically a comparative study of an experimental intervention against some control intervention (or no intervention) that is not a randomized controlled trial. There are many possible types of non-randomized intervention study, including cohort studies, case-control studies, controlled before-and-after studies, interrupted-time-series studies and controlled trials that do not use appropriate randomization strategies (sometimes called quasi-randomized studies).
  • Non-regular sexual partner
    • A non-marital and non-cohabiting partner.
  • Non-systematic review
    • A review or meta-analysis that either did not perform a comprehensive search of the literature and contains only a selection of studies on a clinical question, or did not state its methods for searching and appraising the studies it contains.
  • Nontherapeutic human experimentation
    • MeSH
      Human experimentation that is not intended to benefit the subjects on whom it is performed. Phase I drug studies (clinical trials, phase I) and research involving healthy volunteers are examples of nontherapeutic human experimentation.
  • No-observed-adverse-effect level
    • MeSH
      The highest dosage administered that does not produce toxic effects. The NOAEL will depend on how closely dosages are spaced (lowest-observed-adverse-effect level and no-observed-effect level) and the number of animals examined. The ultimate objective is usually to determine not the "safe" dosage in laboratory animals but the "safe" dosage for humans. Therefore, the extrapolation most often required of toxicologists is from high-dosage studies in laboratory animals to low doses in humans.
  • Normal curve
    • A bell-shaped curve that results when a normal distribution is graphed.
  • Normal distribution
    • MeSH - Wikipedia
      A statistical distribution with known properties commonly used as the basis of models to analyze continuous data. Key assumptions in such analyses are that the data are symmetrically distributed about a mean value, and the shape of the distribution can be described using the mean and standard deviation.
      The symmetrical clustering of values around a central location. The properties of a normal distribution include the following: (1) It is a continuous, symmetrical distribution; both tails extend to infinity; (2) the arithmetic mean, mode, and median are identical; and, (3) its shape is completely determined by the mean and standard deviation.
      Continuous frequency distribution of infinite range. Its properties are as follows: 1, continuous, symmetrical distribution with both tails extending to infinity; 2, arithmetic mean, mode, and median identical; and 3, shape completely determined by the mean and standard deviation.
      Also called Gaussian distribution.
  • Normal distribution curve
    • Wikipedia
      A bell-shaped curve of the frequency distribution of the data.
  • Not significant/non-significant
    • In Clinical Evidence, not significant means that the observed difference, or a larger difference, could have arisen by chance with a probability of more than 1/20 (i.e. 5%), assuming that there is no underlying difference. This is not the same as saying there is no effect, just that this experiment does not provide convincing evidence of an effect. This could be because the trial was not powered to detect an effect that does exist, because there was no effect, or because of the play of chance. If there is a potentially clinically important difference that is not statistically significant then do not say there was a non-significant trend. Alternative phrases to describe this type of uncertainty include, "Fewer people died after taking treatment x but the difference was not significant" or "The difference was not significant but the confidence intervals covered the possibility of a large beneficial effect" or even, "The difference did not quite reach significance."
  • Null hypothesis
    • Wikipedia
      The statistical hypothesis that one variable (e.g. which treatment a study participant was allocated to receive) has no association with another variable or set of variables (e.g. whether or not a study participant died), or that two or more population distributions do not differ from one another. In simplest terms, the null hypothesis states that the factor of interest (e.g. treatment) has no impact on outcome (e.g. risk of death).
      The first step in testing for statistical significance in which it is assumed that the exposure is not related to disease.
  • Null result
    • Wikipedia
      A nonsignificant result; no statistically significant difference between groups.
  • Nulligravida
    • Wikipedia
      A woman who has never been pregnant.
  • Nullipara
    • A woman who has never given birth to a child.
  • Number needed to harm
    • Wikipedia
      An epidemiological measure that indicates how many patients need to be exposed to a risk-factor over a specific period to cause harm in one patient that would not otherwise have been harmed. It is defined as the inverse of the attributable risk. Intuitively, the lower the number needed to harm, the worse the risk-factor.
      A number needed to treat to benefit associated with a harmful effect. It is an estimate of how many people need to receive a treatment before one more person would experience a harmful outcome or one fewer person would experience a beneficial outcome.
  • Number needed to screen
    • The number of patients who would need to be screened to prevent one adverse event.
  • Number needed to treat
    • Wikipedia
      The number needed to treat (NNT) is an epidemiological measure used in assessing the effectiveness of a health-care intervention, typically a treatment with medication. The NNT is the number of patients who need to be treated in order to prevent one additional bad outcome (i.e. the number of patients that need to be treated for one to benefit compared with a control in a clinical trial). It is defined as the inverse of the absolute risk reduction.
      The number of patients who need to be treated over a specific period of time to achieve one additional good outcome. When discussing NNT, it is important to specify the intervention, its duration, and the desirable outcome. It is the inverse of the absolute risk reduction (ARR), expressed as a percentage (100/ARR).
  • Number needed to treat for a meta-analysis
    • Absolute measures are useful at describing the effort required to obtain a benefit, but are limited because they are influenced by both the treatment and also by the baseline risk of the individual. If a meta-analysis includes individuals with a range of baseline risks, then no single NNT will be applicable to the people in that meta-analysis, but a single relative measure (odds ratio or relative risk) may be applicable if there is no heterogeneity. In Clinical Evidence, an NNT is provided for meta-analysis, based on a combination of the summary odds ratio (OR) and the mean baseline risk observed in average of the control groups.
  • Number of community health workers
    • Total number of community health workers in the country.
  • Number of days/years gained or lost
    • A measure of the efficacy of a treatment or habit in terms of increase or decrease in life expectancy.
  • Number of environment and public health workers
    • Total number of environment and public health workers in the country.
  • Number of infant deaths, reported
    • The number of deaths in children under 1 year of age in a given year, for a given country, territory, or geographic area, expressed as number of deaths, as reported from the national health authority.
  • Number of maternal deaths, reported
    • The number of maternal deaths in a given year and the number of live births in that same year for a given country, territory, or geographic area, as reported from the national health authority. Maternal death is defined as the death of a woman while pregnant or within the 42 days after termination of that pregnancy, regardless of the length and site of the pregnancy, due to any cause related to or aggravated by the pregnancy itself or its care, but not due to accidental or incidental causes.
  • Number of nursing and midwifery personnel
    • Total number of nursing and midwifery personnel in the country.
  • Number of other health service providers
    • Total number of other health service providers in the country (excepting physicians, nursing and midwifery personnel, dentistry personnel and community health workers).
  • Number of outpatient care facilities
    • The number of outpatient health care facilities, affiliated to all health institutions, in operation during a given year, for a given country, territory, or geographic area. Outpatient health care is defined as any professional encounter or contact, as an act of health service, between a non-hospitalized individual and a health worker responsible for the evaluation, diagnosis, treatment, or referral of that person in that encounter. Outpatient health care facility is defined as any type of physical area primarily designated to deliver outpatient health care services. Institutional affiliation includes any outpatient health care facility managed by the Ministry of Health or by a governmental equivalent, by Social Security systems, including those for the Army and Police Forces, and by private, for-profit or non-profit, voluntary-driven or not, organizations.
  • Number of physicians
    • Total number of medical doctors (physicians) in the country.
  • Numerical variables
    • Data expressed in numbers.
  • Nuptiality
    • The frequency, characteristics, and dissolution of marriages in a population.
  • Nurse
    • MeSH - Wikipedia
      A nurse is a healthcare professional who, in collaboration with other members of a health care team, is responsible for: treatment, safety, and recovery of acutely or chronically ill individuals; health promotion and maintenance within families, communities and populations; and, treatment of life-threatening emergencies in a wide range of health care settings. Nurses perform a wide range of clinical and non-clinical functions necessary to the delivery of health care, and may also be involved in medical and nursing research.
      WHO Statistical Information System: includes professional nurses, auxiliary nurses, enrolled nurses and other nurses, such as dental nurses and primary care nurses.
      Professionals qualified by education at an accredited school of nursing and licensed by state law to practice nursing. They provide services to patients requiring assistance in recovering or maintaining their physical or mental health.
  • Nursing administration research
    • MeSH
      Research concerned with establishing costs of nursing care, examining the relationships between nursing services and quality patient care, and viewing problems of nursing service delivery within the broader context of policy analysis and delivery of health services.
  • Nursing audit
    • MeSH
      A detailed review and evaluation of selected clinical records by qualified professional personnel for evaluating quality of nursing care.
  • Nursing care
    • MeSH
      Care given to patients by nursing service personnel.
  • Nursing education research
    • MeSH
      Investigations into the problems of integrating research findings into nursing curricula, developing problem solving skills, finding approaches to clinical teaching, determining the level of practice by graduates from different basic preparations, etc.
  • Nursing ethics
    • MeSH - Wikipedia
      A branch of applied ethics that concerns itself with activities in the field of nursing. Nursing ethics shares many principles with medical ethics, such as beneficence, non-maleficence and respect for autonomy. It can be distinguished by its emphasis on relationships, maintaining dignity and collaborative care.
      The principles of proper professional conduct concerning the rights and duties of nurses themselves, their patients, and their fellow practitioners, as well as their actions in the care of patients and in relations with their families.
  • Nursing evaluation research
    • MeSH
      Research carried out by nurses that uses interviews, data collection, observation, surveys, etc., to evaluate nursing, health, clinical, and nursing education programs and curricula, and which also demonstrates the value of such evaluation.
  • Nursing methodology research
    • MeSH
      Research carried out by nurses concerning techniques and methods to implement projects and to document information, including methods of interviewing patients, collecting data, and forming inferences. The concept includes exploration of methodological issues such as human subjectivity and human experience.
  • Nursing research
    • MeSH - Wikipedia
      The term used to describe the evidence used to support nursing practice.
      Research carried out by nurses, generally in clinical settings, in the areas of clinical practice, evaluation, nursing education, nursing administration, and methodology.