N

N
Number of cases. Uppercase "N" refers to the number of cases in the population. Lower case "n" refers to the number of cases in the sample.

Nominal Variable
A quantitative variable whose attributes have no inherent order. FOR EXAMPLE, "sex" or "race."

Nonequivalent Comparison Group Design
Evaluation designs that use nonrandomized comparison groups to evaluate program effects. Also referred to as quasi-experimental designs.

Non-experimental Data
Data not produced by an experiment or quasi-experiment. FOR EXAMPLE, the data may be administrative records or the results of a survey.

Nonindex Crimes
Part 2 crimes under the Uniform Crime Reporting System. Twenty-two crimes are included, such as simple assault, vandalism, gambling, drunkenness, and the like. (See Index Crimes.)

Non-probability Sample
A sample not produced by a random process. FOR EXAMPLE, it may be a sample based upon an evaluator's judgment about which cases to select.

Non-respondent
A person who fails to answer either a questionnaire or a question.

Non-response Bias
The bias created by the failure of part of a sample to respond to a survey or answer a question. If those responding and those not responding have different characteristics, the responding cases may not be representative of the population from which they were sampled.

Normal Distribution (Curve)
A theoretical distribution that is closely approximated by many actual distribution of variables.

Normative Question
A type of evaluation question requiring comparison between what is happening (the condition) to norms and expectations or standards for what should be happening (the criterion).

Null Hypothesis
A hypothesis stating that two variables are not related. Research attempts to disprove the null hypothesis by finding evidence of a relationship.