Newman-Keuls test - The Newman-Keuls test, also called the Student-Newman-Keuls test, is a stepwise procedure for comparing group means.
Neyman - Pearson lemma - The Neyman - Pearson lemma identifies a most powerful statistical test for a fully specified null distribution against a fully specified alternative...
Noise factor - A noise factor is a process input or operating condition that is difficult, inconvenient or impractical to control in normal use.
Noisy channel model - A noisy channel model explains an observed signal as the result of an underlying message passing through a process that can alter it.
Nominal scale - A nominal scale classifies observations into categories without assigning those categories an inherent order or numerical distance.
Nominal significance level - A nominal significance level is the stated significance threshold for a statistical test, commonly written as alpha.
Non-central F distribution - The non-central F distribution is the distribution of a ratio formed by dividing an independent noncentral chi-square variable and a central chi-square...
Non-equivalent groups design - A non-equivalent groups design compares intervention and comparison groups that were not formed by random assignment and may differ in important ways before...
Non-inferiority study - A non-inferiority study is designed to assess whether a new intervention performs no worse than a comparator by more than a prespecified acceptable margin.
Non-linear estimation - Non-linear estimation is the process of estimating unknown quantities in a model when the parameter relationships or estimation problem require nonlinear...
Non-random (non-probability) sample - A non-random, or non-probability, sample is a collection of units selected without a probability sampling design that gives population members known...
Non-sampling error - Non-sampling error is error in statistical information arising from sources other than the random variation caused by observing a sample instead of the full...
Noncentrality parameter - A noncentrality parameter is a parameter that distinguishes a noncentral probability distribution from its central counterpart.
Nondirectional test - A nondirectional test is a statistical hypothesis test designed to detect departures from the null hypothesis in either direction.
Nonhomogeneous Gaussian regression - Nonhomogeneous Gaussian regression is a statistical method that converts ensemble forecasts into a Gaussian predictive distribution whose mean and variance...
Nonlinear modeling - Nonlinear modeling is the construction and use of models that represent relationships beyond a simple constant-rate, additive response.
Nonlinear regression - Nonlinear regression models the relationship between an outcome and one or more predictors using a function that is nonlinear in at least some unknown...
Nonparametric estimator - A nonparametric estimator is a rule for estimating a population quantity without restricting the entire population distribution to a particular...
Nonparametric tests - Nonparametric tests are statistical hypothesis tests that avoid specifying a particular parametric distribution for the data, or make relatively limited...
Nonresponse - Nonresponse occurs when information intended to be collected from an eligible unit is not obtained or is incomplete.
Nonresponse error - Nonresponse error is the error in a statistical result attributable to information not being obtained from units or items intended to be observed.
Normal distribution - The normal distribution, also called the Gaussian distribution, is a continuous probability distribution with a symmetric bell-shaped density.
Normal equations - The normal equations are the linear equations that characterize a least-squares solution.
Normal matrix - A normal matrix is a square matrix that commutes with its conjugate transpose: AA* = A*A.
Normality - Normality is the property or modeling assumption that a relevant random quantity follows a normal, or Gaussian, distribution.
Normality in arrays - Normality in arrays is a traditional statistical term for the assumption that the distribution of a response Y is normal at each fixed value of a predictor X.
Normalization - Normalization is a transformation that puts values into a specified scale or mathematical form.
Normalized Discounted Cumulative Gain - Normalized Discounted Cumulative Gain, usually abbreviated NDCG, is a ranking metric that compares the relevance achieved by a predicted ordering with the...
Normalized utilities - Normalized utilities are utility values placed on a specified reference scale, commonly zero for a chosen worst outcome and one for a chosen best outcome.
Null distribution - A null distribution is the probability distribution of a test statistic under a specified null hypothesis and the accompanying assumptions.
Null hypothesis - A null hypothesis is a statistical claim used as the reference for a hypothesis test.
Null result - A null result is an informal description of a study that does not provide the expected or statistically significant evidence for an effect or association.
Number needed to treat - The number needed to treat, usually abbreviated NNT, expresses an absolute difference in outcome probabilities as the expected number of people who would...
Number raised estimation - Number raised estimation is a survey estimation method that expands sample observations using a common population-to-sample count ratio within each sampling...
Numeric variable - A numeric variable is a variable whose values represent quantities that are counted or measured.
O'Brien - Fleming boundary - An O'Brien - Fleming boundary is a group-sequential testing boundary that requires especially strong evidence for early rejection of a null hypothesis and...
Object model - In the perception sense used here, an object model represents properties of the objects that may occur in a visual environment.
Observed frequencies - Observed frequencies are the counts actually recorded in categories, intervals, or cells of a frequency table.
Observer-expectancy effect - The observer-expectancy effect occurs when an observer's or researcher's expectations influence the behavior being studied or the way observations are...
Odds - Odds express the probability that an event occurs relative to the probability that it does not occur. If the event probability is p, its odds are p/(1 − p).
Odds ratio - An odds ratio compares the odds of an event in one group or condition with the odds in another.
Off-line SPC - Off-line SPC refers to statistical process-control techniques used to characterize or improve a process without necessarily deciding, as each new...
Omega squared ( w 2 ) - Omega squared, conventionally written omega² or ω², is an effect-size measure used with analysis of variance to estimate the proportion of outcome variation...
Omitted-variable bias - Omitted-variable bias occurs when leaving a relevant variable out of a statistical model distorts the estimated relationship for an included variable...
Omnibus test - An omnibus test evaluates a broad null hypothesis that combines several restrictions or comparisons into one overall test.
On-line SPC - On-line SPC means statistical process control used to monitor an operating process and identify when its behavior warrants investigation or corrective...
One-factor-at-a-time method - The one-factor-at-a-time method, often abbreviated OFAT, investigates a system by changing one input factor while holding the others fixed.