
Constructs
Internal attributes or characteristics that cannot be directly observed but are useful for describing and explaining behavior

continuous variable
An infinite number of possible values that fall between any two observed values. A continuous variable is divisible into an infinite number of fractional parts.

control condition
Individuals who do not receive the experimental treatment. Instead, they either receive no treatment or they receive a neutral, placebo treatment. The purpose of a control condition is to provide a baseline for comparison with the experimental condition.

correlational method
Two different variables are observed to determine whether there is a relationship between between them.

data
A collection of measurements or observations.

datum
A single measurement or observation and is commonly called a score or raw score.

dependent variable
The variable that is observed to assess the effect of the treatment.

descriptive statistics
Statistical procedures used to summarize, organize, and simplify data.

discrete variable
Consists of separate, indivisible categories. No values can exist between two neighboring categories.

experimental condition
Individuals who do receive the experimental treatment.

experimental method
One variable is manipulated while another variable is observed and measured. To establish a causeandeffect relationship between the two variables, an experiment attempts to control all other variables to prevent them from influencing the results.

independent variable
The variable that is manipulated by the researcher. In the behavioral research, the independent variable usually consists of the two (or more) treatment conditions to which subjects are exposed. The independent variable consists of the antecedent conditions that are manipulated prior to observing the dependent variable.

inferential statistics
techniques that allow us to study samples and then make generalizations about the populations from which they were selected.

interval scale
Ordered categories that are all intervals of exactly the same size. Equal differences between numbers on scale reflect equal differences in magnitude. However, the zero point on an interval scale is arbitrary and does not indicate a zero amount of the variable being measured.

lower real limit
the bottom of the interval (for continuous variables)

operational definition
Identifies a measurement procedure (a set of operations) for measuring an external behavior and uses the resulting measurements as a definition and a measurement of a hypothetical construct. Note that an operational definition has two components: first, it describes a set of operations for measuring a construct. second, it defines the construct in terms of the resulting measurements.

ordinal scale
A set of categories that are organized in an ordered sequence. Measurements on an ordinal scale rank observations in terms of size or magnitude.

parameter
Avalue, usually a numeric value, that describes a population. A parameter is usually derived from measurements of the individuals in the population.

population
the set of all the individuals of interest in a particular study

quasiindependent experiment
in a nonexperimental study, the "independent variable" that is used to create the different groups of scores is often called this

ratio scale
An interval scale with the additional feature of an absolute zero point. With a ratio scale, ratios of numbers do reflect ratios of magnitude.

real limits
The boundaries of intervals for scores that are represented on a continuous number line. The real limit separating two adjacent scores is located exactly halfway between the scores.

sample
a set of individuals selected from a population, usually intended to represent the population in a research study

sampling error
the discrepancy, or amount of error, that exists between a sample statistic and the corresponding population parameter

statistic
a set of mathematical procedures for organizing, summarizing, and interpreting information

upper real limit
the top of the interval (for continuous variables)

variable
a characteristc or condition that changes or has different values for different individuals

frequency distribution
an organized tabulation of the number of individuals located in each category on the scale of measurement

negatively skewed
a skewed distribution with the tail pointed to the lefthand side (below zero)

positively skewed
a skewed distribution with the tail pointing to the ridehand side (above zero)

skewed distribution
the score tends to pile up toward one end of the scale and taper off gradually at the other end

symmetrical distribution
it is possible to draw a vertical line through the middle so that one side of the distribution is a mirror image of the other

tail
the section where the scores taper off toward one end of a distribution

central tendency
A statistical measure to dtermine a single score that define the center of a distribution. The goal of central tendency is to find the single score that is most typical or most representative of the entire group.

mean
the sum of the scores, divided by the number of scores

median
if the scores in a distribution are listed in order from smallest to largest, it is the midpoint of the list

mode
in a frequency distribution, this is the score or category that has the greatest frequency

