Chapter 1: Introduction to Statistics


a set of mathematical procedures for organizing, summarizing and interpreting info.


set of all individuals of interest in a particular study


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


characteristic/condition that changes or has different values for different individuals

data (plural)


data set

collection of measurements/observations

datum (singular)

single measurement/observation and is commonly called a score/raw score


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


a value, usually a numerical value, 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

consists 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

control condition

Individuals 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.

experimental condition

Individuals that do receive the experimental treatment.

quasi-independent variable

In a nonexperimental study, the "independent variable" that is used to create the different groups of scores


internal attributes/characteristics that cannot be directly observed but are useful for describing and explaining behavior

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, i

discrete variable

consists of separate, indivisible categories. NO values can exist b/n 2 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 halfway between the scores. Each score has two real limits. The upper real limit is the top of the in

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.

ordinal scale

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

interval scale

consists of ordered categories that are all intervals of exactly the same size. Equal differences b/n 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

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.

experimental method

one variable is manipulated while another variable is observed and measured. To establish a cause-and-effect 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 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 tha

dependent variable

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