POLS 209: Introduction to Political Science Research C1-2, 4, and 6 Concepts

causal

implying causality (the relationship between cause and effect; the principle that everything has a cause)

correlation

a statistical measure of covariation which summarizes the direction (positive or negative) and strength of the linear relationship between two variables

covary

when two variables vary together

data

a collection of variable values for at least two observations

dependent variable

a variable for which at least some of the variation is theorized to be caused by one or more independent variables

empirical

based on real-world observations

independent variable

a variable that is theorized to cause variation in the dependent variable

measure

a process by which abstract concepts are turned into real-world observations

negative relationship

higher values of the independent variable tend to coincide with lower values of the dependent variable

normative statements

statements about how the world ought to be

null hypothesis

a theory-based statement about what we would observe if there were no relationship between an independent variable and the dependent variable

operationalize

another word for measurement; when a variable moves from the concept level in a theory to the real-world measure for a hypothesis test

paradigm

a shared set of assumptions and accepted theories in a particular scientific field

paradigm shift

when new findings challenge the conventional wisdom of a paradigm to the point where the set of shared assumptions and accepted theories in a scientific field is redefined

parsimonious

synonym for simple or succinct

positive relationship

higher values of the independent variable tend to coincide with higher values of the dependent variable

theoretical model

the combination of independent variables, the dependent variable, and the causal relationships that are theorized to exist between them

theory

a tentative conjecture about the causes of some phenomenon of interest

variable

a definable quantity that can take on two or more values

variable label

the label used to describe a particular variable

variable values

the values that a particular variable can take on

aggregate

a quantity that is created by combining the values of many individual cases

consumer confidence

a subjective assessment by members of the mass public that registers the public’s optimism or pessimism about the state of the economy

control group

in an experiment, the subset of cases that is not exposed to the main causal stimulus under invedtigation

cross-sectional observational studies

a research design that focuses on variation across spatial units at a single time unit

external validity

the degree to which we can be confident that the results of our analysis apply not only to the participants and circumstances in the study, but also to the population more broadly consumed

field experiment

an experimental study that occurs in the natural setting where the subjects normally lead their lives

internal validity

the degree to which a study produces high levels of confidence about whether the independent variable causes the dependent variable

natural experiment

situations in nature that are not properly defined as experiments but the values of the independent variable arise naturally in such a way as to make it seem as if true random assignment by a researcher has occurred

placebo

in an experiment, a harmless stimulus given to the control group

random assignment

when the participants for an experiment are assigned randomly to one of several possible values of X, the independent variable

random sampling

a method for selecting individual cases for a study in which every member of the underlying population has an equal probability of being selected

replication

a scientific process in which researchers implement the same procedures repeatedly in identical form to see if the relationships hold in a consistent fashion

research designs

the strategies that a researcher employs to make comparisons with the goal of evaluating causal claims

sample convenience

a sample of cases from the underlying population in which the mechanism for selecting cases is not random

spatial unit

the physical unit that forms the basis for observation

time-series observational studies

a research design that focuses on variation within a single spatial unit over multiple time units

time unit

the time-based unit that forms the basis for observation

treatment group

in an experiment, the subset of cases that is exposed to the main causal stimulus under investigation

categorical variable

a variable for which cases have values that are either different from or the same as the values for other cases, but about which we cannot make any universally holding ranking distinction

continuous variable

a variable whose metric has equal unit differences such that a one-unit increase in the value of the variable indicates the same amount of change across all values of that variable

equal unit differences

a variable has equal unit differences if a one-unit increase in the value of that variable always means the same thing

measurement metric

the type of values that the variable takes on

ordinal variable

a variable for which we can make universally holding ranking distinctions across the variable values, but whose metric does not have equal unit differences