### Magnitude

Characteristic of a scale of measurement where the individual units possess the qualities of greater than, equal to, or less than.

### Main Effect

The effect of one variable on another without any other variables or subgroups involvement.

### Manifest Content

According to Freud, the story-like superficial content of a dream, often representing only the daily activities and little underlying unconscious material.

### Maslow, Abraham

Humanistic Theorist most famous for the development of the Hierarchy of Needs.

### Maturation

Changes due to the natural process of aging as determined by your genetics

### Mean

A measure of central tendency determined by adding all scores together and dividing by the number of scores. Often referred to as the statistical average.

### Measure of Central Tendency

An average (see Mean, Median, and/or Mode)

### Measurement, Scales of

Categories of data based on their numerical characteristics (See Ratio, Interval, Ordinal, and Nominal Scales)

### Median

A measure of central tendency that uses the middle most occurring score in a distribution (the score that occurs at exactly the 50th percentile).

### Medulla Oblongata

Part of the brainstem that controls vital life-sustaining functions such as heartbeat, breathing, blood pressure, and digestion.

### Memory Effect

Error in research that results from subjects recalling previous testing and applying that knowledge to current testing.

### Mesokurtic

A curve or distribution that has a balanced amount of variance so that is resembles a normal curve.

### Meta Analysis

The statistical procedure used to combine numerous and independent research results into one study. Each research study becomes one subject in the meta-analysis.

### Minnesota Multiphasic Personality Inventory, 2nd. Edition

An Objective test utilizing 567 items which have been empirically derived to measure a variety of psychological concerns.

### MMPI-2

See Minnesota Multiphasic Personality Inventory, 2nd. Edition.

### Mode

A measure of central tendency that uses the most frequently occurring score. A distribution with two or more scores that are equal and occur most frequently is called multi-modal.

### Modeling

Learning through the imitation or observation of others.

### Mortality

Subject drop-out in a research study. Mortality becomes a problem when a disproportionate drop out rate occurs between two or more groups (Example: 30% of males drop out of group one while only 2% of males drop out in group two, resulting in uneven groups).

### Motivation

The process that energizes and/or maintains a behavior.

### Motive

Internal states that provide direction for one’s behaviors.

### Multiple Correlation

A correlational technique used when there is one X and two or more Y. (Example: the correlation between age and (math and English ability).