Statistics
A set of mathematical procedures for organizing, summarizing, and interpreting information.
Population
The set of all the individuals of interest in a particular study.
Sample
A set of individuals selected from a population, usually intended to represent the population in a research study.
Variable
A characteristic or condition that changes or has different values for different individuals.
Data (plural)
Measurements or observations
Data Set
A collection of measurements or observations
Datum (singular)
A single measurement or observation, aka score/raw score
Raw Score
A single measurement or observation, aka Datum
Parameter
(Population) A value, usually numerical, that describes a population. Usually derived from the measurements of the individuals in the population.
Statistic
(Sample) A value, usually numerical, that describes a sample. Usually derived from the measurements of the individuals in a sample.
Descriptive Statistics
Statistical procedures used to summarize, organize, and simplify data.
Inferential Statistics
Techniques that allow us to study samples and then make generalizations about the populations from which they were derived.
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.
Experimental Method
One variable is MANIPULATED, while another variable is observed and measured.
Independent Variable
Variable that is manipulated by the researcher, usually consisting of the two (or more) treatment conditions to which subjects are exposed. (Antecedent conditions that were manipulated prior to observing the dependent variable).
Dependent Variable
One that is observed to assess the effect of the treatment.
Control Condition
Do not receive the experimental treatment. Instead, they either receive no treatment or they receive a neutral, placebo treatment.
Experimental Condition
Individuals that receive the experimental treatment.
Quasi-Independent Variable
In a non-experimental study, the "independent variable" that is used to create the different groups of scores.
Construct
Internal attributes (such as intelligence, anxiety, and hunger) that cannot be directly observed by are useful for describing and explaining behavior. Intangible; Cannot be directly observed.
Operational Definition
Identifies a measurement procedure for measuring for measuring external behavior, using the resulting measurements as a definition and a measurement of a hypothetical construct. Has two components... 1. It describes a set of operations for measuring a con
Discrete Variable
Consists of separate, indivisible categories. No values can exist between two neighboring categories.
Continuous Variable
(interval, ratio) An infinite number of possible values that fall between any two observed values (fractions & decimals). Is divisible into an infinite number of fractional parts.
Real Limits
Boundaries of intervals for scores that are represented on a continuous number line (located exactly halfway between the scores, thus having two limits (upper limit, lower limit). Ex - time of 31.1 seconds = upper 31.15, lower 31.05.
Upper Real Limit
Top of the interval
Lower Real Limit
Bottom of the interval
Nominal Scale
A set of categories that have different names- categorized but not quantified distinctions between observations. Ex - Academic Majors, sports teams.
Ordinal Scale
A set of categories that are organized in an ordered sequence (names and fixed order) ranked by size or magnitude. Ex - 1st, 2nd, 3rd, or small, medium, large.
Interval Scale
Arbitrary value for zero; consists of ordered categories that are all intervals of exactly the same size with equal difference between numbers representing equal differences in magnitude. Ex- Temperature.
Ratio Scale
An interval scale with the additional feature of an absolute zero point. Determines direction and size of difference. Ex- height, weight, reaction time, test errors.