
Statistics
Refers to a set of mathematical procedures for organizing, and interpreting information

Population
The set of all the individuals of interest in a particular study

Sample
Set of individuals selected from a population, usually intended to represent the population in a research study

Variable
Characteristic or condition that changes or has different values for different individuals

Data
 plural: Measurements or observations

Data Set
Collection of measurements or observations

Datum
Singular: Single measurement or observation and is commonly called a score or raw score

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

Statistic
A value, usually numerical, that describes a sample. A statistic is usually derived from measurements of the individuals in the sample.

Descriptive Statistics
Statistical procedures used to summarize, organize, and simplify data

Inferential Statistics
Consist of techniques that allow us to study samples and then make generalizations about the populations from which they were selected.

Sampling Error
The discrepancy, or amount of error, that exists between a sample statistic and the corresponding population parameter.

Correlational Method
Two different variables are observed to determine whether there is a relationship between them

Manipulation
Researcher manipulates one variable by changing it's value from one level to another. A second variable is observed (measured) to determine whether the manipulation causes changes to occur

Control
Researcher must exercise control over the research situation to ensure that other, extraneous variables do not influence the relationship being examined.

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

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

Dependent Variable
The variable that is being observed to assess the effect of the treatment

Control Condition
 The individuals within the condition do not receive the experimental treatment.
 Instead, they receive no treatment or they receive a neutral, placebo treatment.
 The purpose of the control condition is to provide a baseline for comparison with the experimental condition

Experimental Condition
The individuals that receive the experimental treatment

QuasiIndependent Variable
the "independent variable" in a nonexperimental study that is used to create different groups of scores
Cannot be manipulated  Male/Female, Time etc

Operational Definition
Defines a constructs in terms of external behaviors that can be observed and measured

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

Operational definition
 identifies a measurement procedure (set of operations) for measuring an external behavior and uses the resulting measurements as a definition and a measurement of a hypothetical construct.
 OD has two components:
 1) Describes a set of operations for measuring a construct
 2) Defines the construct in terms of the resulting measurements

Discrete Variable
 Consists of separate, indivisible categories.
 No values can exist between two neighboring categories

Continuous Variable
 There are 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

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 half way between the scores.
 Each score has two real limits:
 The upper limit is at the top of the interval
 The lower limit is at the bottom

Nominal Scale
 Consists of a set of categories that have different names.
 Measurements on a nominal scale label and categorize observations, but do not make any quantitative distinctions between observations.
 Race, gender, occupation etc.

Ordinal Scale
Consists of a set of categories that are organized in an ordered sequence. Measurements on an ordinal scale ran observations in terms of size and magnitude

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

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

