PSYC STATS EXAM 1 NOTES.docx

Variable

A characteristic that can change or take on different values.

Population

An entire group of individuals that is defined.

Sample

A subset used to represent a population.

Inferential Statistics

Use sample data to make general conclusions about populations.

Descriptive Statistics

Methods for organizing and summarizing data.

Sampling Error

The discrepancy between a sample statistic and its population parameter.

Discrete Variables

Variables consisting of indivisible categories.

Continuous Variables

Variables that are infinitely divisible into any unit.

Nominal Scale

An unordered set of categories identified by name only.

Ordinal Scale

An ordered set of categories indicating direction of difference.

Interval Scale

An ordered set of equal-sized categories with meaningful intervals.

Ratio Scale

Like interval scale, but with a meaningful zero point.

Correlation

Indicates the strength and direction of the relationship between two variables.

Independent Variable

The condition or event that is manipulated by the experimenter.

Dependent Variable

The aspect or behavior thought to be affected by the independent variable.

Standard Deviation

A measure of the average distance of scores from the mean.

Z-Score

Expresses data in terms of the mean and standard deviation.

Frequency Distribution

A summary of how often each category of a variable occurs.

Percentile Rank

The percentage of individuals with scores equal to or less than a given X value.

Mean

The arithmetic average computed by summing all scores and dividing by the number of scores.

Median

The middle score that divides the distribution so that 50% are above and below.

Mode

The most frequently occurring score or class interval in a distribution.

Variance

The average squared deviation from the mean.

Normal Distribution

A symmetrical distribution with greatest frequency in the middle.

Bimodal Distribution

A distribution with two modes.

Skewed Distribution

A distribution where scores pile up on one side, leaving a tail on one end.

Stem and Leaf Display

A method for displaying a frequency distribution that separates each score into two parts.

Range

The difference between the highest and lowest scores in a dataset.

Central Tendency

A statistical measure that uses a single value to describe the center of a distribution.