Dictionary

N

Net Survival ModelConceptNet Survival Estimation, Population-Cause Survival Model

A survival model estimating the survival a population would experience if the disease studied were the only possible cause of death.

Network AdequacyTermNetwork Sufficiency, Adequate Provider Access

A regulatory standard requiring a plan's provider network include enough providers, within reasonable distance and wait time, to meet enrollee needs.

Network DesignTermNetwork Configuration, Plan Network Build

The process of selecting and contracting with providers for a plan's network, balancing cost, quality, and geographic coverage.

Network GeometryTermNetwork Shape, Evidence Network Structure

The overall structure and pattern of connections formed by trials in a network meta-analysis, showing which treatments were compared directly.

Network Meta-AnalysisConceptNMA, Multiple-Treatments Meta-Analysis, Mixed Treatment Comparison, MTC

Network meta-analysis (NMA) compares three or more treatments in one analysis, pooling direct and indirect trial evidence to inform HTA decisions.

Network Meta-Analysis HTAConceptNMA in HTA, NMA for Reimbursement

The application of network meta-analysis specifically within health technology assessment, generating comparative effectiveness estimates when treatments were never studied together.

Network ModelTermGraph-Based Simulation

A managed care structure where a plan contracts with a broad network of independent providers, rather than employing them directly.

Network ReferralTermIn-Plan Referral, Directed Referral

A referral from a provider to another within their contracted insurance network, generally resulting in lower patient cost-sharing.

Neurological Disease EconomicsTermNervous-System Disease Economics, Neurological Economics

The broad application of health economic evaluation to conditions affecting the brain, spinal cord, and nervous system, spanning neurodegenerative disease, epilepsy, and injury.

Neurological ResponseTermNeuro Response, Nervous System Response

A biomarker or clinical outcome measure indicating a change in neurological function or structure, such as improved neurological examination or imaging findings.

Neuropathic PainTermNerve Pain, Neuralgia

Chronic pain arising from damage or dysfunction of the nervous system itself, rather than ongoing tissue injury, often burning or shooting in character.

Never EventTermSerious Preventable Event, Zero-Tolerance Event

A serious, largely preventable safety event that should essentially never occur if established protocols are followed, such as wrong-site surgery.

Newborn ScreeningTermNeonatal Screening, Heel-Prick Screening

A public health programme testing newborns shortly after birth for serious, typically treatable conditions before symptoms would otherwise appear.

Newton-Raphson MethodConceptNewton-Raphson, Newton Iteration

The Newton–Raphson method is an iterative numerical algorithm that uses local derivative information to find a root of an equation.

NICETermNational Institute for Health and Care Excellence, National Institute for Clinical Excellence

The National Institute for Health and Care Excellence, conducting assessment and developing guidelines for the NHS in England and, for some functions, Wales.

NICE ThresholdTermNICE Cost-Effectiveness Threshold, NICE QALY Threshold

The NICE threshold is the £25,000 to £35,000 per QALY gained range NICE committees use to judge whether an ICER is an effective use of NHS resources.

Nocebo EffectTermNocebo Response, Negative Expectation Effect

A phenomenon in which a patient experiences a harmful outcome purely from their expectation of harm, rather than any pharmacological effect.

Node-SplittingConceptNode-Split Model, Inconsistency Check

A technique testing for inconsistency in a network meta-analysis by separately estimating direct and indirect evidence for one comparison and comparing them.

Nominal CostTermCurrent-Price Cost, Money-Terms Cost

A cost expressed in the prices of the period in which it was actually incurred, without adjustment for inflation.

Nominal Group TechniqueTermNGT, Structured Group Judgement

A structured method eliciting and prioritising group ideas through individual silent generation followed by structured discussion and ranked voting.

Nominal ScaleConceptNominal Measurement, Nominal Level of Measurement, Nominal Variable

Nominal scale is a level of measurement whose numbers only name categories, such as trial arm or EQ-5D dimension, so counts are valid but averages are not.

Non-AdherenceTermNon-Compliance, Medication Non-Compliance

A patient's failure to take a prescribed medication or follow a regimen as directed, whether unintentional, such as forgetting, or intentional.

Non-Dominated AlternativeTermEfficient Option, Frontier Option

An intervention on the cost-effectiveness frontier, meaning no other option or combination of options is both less costly and more effective.

Non-Excludable GoodsTermNon-Excludable Resource, Open-Access Good

Goods for which it is not possible, or not practical, to stop those who have not paid from consuming their benefits.

Non-Inferiority TrialConceptNI Trial, Non-Inferiority Study

A trial designed to show a new treatment is not meaningfully worse than an active comparator, within a predefined acceptable margin.

Non-Medical SwitchingTermPayer-Driven Switching, Cost-Driven Switching

A situation where a patient's medication is changed for reasons unrelated to clinical response, such as an insurer's formulary change.

Non-Mixture Cure ModelConceptNon-Mixture Cure Rate Model, Bounded Cumulative Hazard Cure Model

An alternative cure model structure formulating survival directly in terms of the cured fraction without explicitly splitting the population into two subgroups.

Non-Parametric AnalysisTermDistribution-Free Analysis, Rank-Based Analysis

Statistical methods not relying on the data following a specific probability distribution, more flexible but sometimes less powerful than parametric methods.

Non-Parametric EstimationConceptDistribution-Free Estimation, Empirical Estimation

A statistical approach to estimating a survival function without assuming the data follow any specific mathematical distribution.

Non-Parametric MethodsTermDistribution-Free Methods, Rank-Based Methods, Non-Parametric Statistics

Statistical techniques making minimal assumptions about the underlying probability distribution, providing a flexible alternative when standard distributional assumptions do not hold.

Non-Parametric SurvivalConceptDistribution-Free Survival, KM-Based Survival

Survival data or estimates obtained without assuming a specific distribution, such as a Kaplan-Meier curve calculated directly from observed trial data.

Non-Preference-Based MeasureTermNon-Preference Measure, Clinical Rating Scale

A health status instrument reporting dimension scores not derived from a preference elicitation exercise, so its scores cannot directly generate quality-adjusted life years.

Non-Preferred DrugTermNon-Formulary Drug

A medication assigned to a higher-cost formulary tier, typically with greater patient cost-sharing than a preferred alternative, to encourage lower-cost use.

Non-Preferred TierTermHigh Cost-Share Tier, Non-Formulary Tier

A formulary or network category with the highest cost-sharing in a tiered design, applied to options an insurer wishes to discourage.

Non-Profit HospitalTermNot-for-Profit Hospital, Charitable Hospital

A hospital organised as a non-profit entity, reinvesting operating surplus rather than distributing it, typically in exchange for tax-exempt status.

Non-Randomised Controlled TrialConceptNon-Randomized Controlled Trial, Non-Randomised Trial

A non-randomised controlled trial is a trial where investigators assign people to treatment or control without chance, so its estimates risk confounding.

Non-Response ErrorTermNon-Response Bias, Unit Non-Response

A survey error arising when selected participants fail to respond, and respondents differ systematically from non-respondents, potentially biasing the results.

Non-Sampling ErrorTermSystematic Survey Error, Coverage-and-Response Error

Any source of error not arising from the specific sample studied, including measurement, coverage, and non-response error, unlike sampling error alone.

Nonlinear ProgrammingConceptNLP (Optimisation), Non-Linear Optimisation

Nonlinear programming is the optimization of an objective function subject to equality, inequality, or bound constraints when the objective or at least one constraint is nonlinear in the decision variables.

Normal DistributionConceptGaussian Distribution, Bell Curve

A normal distribution is a continuous, symmetric probability distribution characterised by a mean that sets its centre and a positive standard deviation that sets its spread.

Northeast QuadrantTermNE Quadrant, More Costly More Effective Quadrant

The region of the cost-effectiveness plane where a new intervention is both more costly and more effective than its comparator.

Northwest QuadrantTermNW Quadrant, Dominated Quadrant

The region of the cost-effectiveness plane where a new intervention is both more costly and less effective than its comparator.

Not Cost-EffectiveTermPoor Value for Money

A judgement that an intervention's ICER exceeds the relevant cost-effectiveness threshold, meaning its extra benefit does not justify its extra cost.

Nottingham Health ProfileConceptNHP

Nottingham Health Profile (NHP) is a generic measure of perceived physical, social and emotional health problems, scored by section, not as a QALY utility.

Nudge InterventionTermNudge, Behavioural Nudge

A feature of choice architecture that predictably alters behaviour without forbidding options or significantly changing economic incentives.

Null HypothesisConceptH0, No-Effect Hypothesis

In hypothesis testing, the default assumption of no true effect or difference between the groups or conditions being compared.

Number Needed to HarmTermNNH, Harm Number

The number of patients who would need exposure to a treatment or risk factor for one additional patient to experience an adverse outcome.

Number Needed to ScreenTermNNS, Screening Number Needed

The number of individuals who would need screening for a condition to prevent one adverse outcome, based on prevalence and programme effectiveness.

Number Needed to TreatConceptNNT, Treatment Number Needed

The reciprocal of a nonzero absolute difference in event risk between an intervention and comparator, interpreted as the expected number treated for one additional beneficial or harmful outcome over a stated period.

Numerical IntegrationConceptQuadrature, Numerical Quadrature

Numerical integration approximates the area represented by a definite integral when an exact antiderivative is unavailable, inconvenient or evaluated from discrete data.