### N

Symbol used for the number of subjects or data in a distribution. A study with 10 subjects would have an N equal to 10.

### Naturalistic Observation

A research method where the subject(s) is(are) observed without interruption under normal or natural circumstances.

### NCE Score

A standard score that sets the mean to fifty and standard deviation to 21.06, allowing the 99th percentile to have a score of 99 and the first percentile a score of 1.

### Negative Correlation

a correlation where one two variables tend to move in the opposite direction (example: the number of pages printed and the amount of ink left in your printer are negatively correlated. The more pages printed, the less ink you have left.)

### Negative Skew

A curve or distribution of scores that has extreme scores below the mean that are atypical of the majority of scores.

### Neuron

A specialized nerve cell.

### Neurotransmitter

A chemical found in animals that plays a role in our behavior, cognitions, and emotions.

### Nightmare

A frightening dream occurring in REM sleep.

### Nominal Scale

Any scale that contains no magnitude. Often nominal is thought of as name only, meaning that the variables of a nominal scale can be identified but not measured.

### Nondeclarative Memory

A subsystem within Long term memory which consists of skills we acquire through repetition and practice (e.g., dance, playing the piano, driving a car)

### Nonparametric Test

Any statistic that is designed for ordinal or nominal data or data that is not normally distributed

### Norepinephrine

A neurotransmitter associated with eating and alertness. Too little has been associated with depression and too much has been associated with schizophrenia.

### Norm

An expectation based on multiple observations.

### Normal Curve

A graphical interpretation of a population that is ‘bell shaped’ as it has the highest frequency in the middle and this frequency diminishes the farther you get from the center on either end. The mean, median, and mode are all equal in a perfect normal curve.

### Normal Distribution

The scores of a sample or population that, when graphed, fall on or close to a normal curve. A normal distribution is often ideal in research because the data can then be said to have all of the characteristics of a normal curve.

### Null Hypothesis

The hypothesis that states there is no difference between two or more sets of data.