Ch. 4 from The Fundamentals of Political Science Research

research designs

strategies to go about testing whether X causes Y

experiment

research design in which the researcher both controls and randomly assigns values of the independent variable to the participants

treatment group

the group in an experimental investigation that is subjected to the change in the independent variable

control group

the group that does not receive the experimental treatment.

internal validity

the extent to which an experiment shows convincingly that changes in behavior are a function of the independent variable and not the result of uncontrolled or unknown variables.

random assignment to treatment groups

when participants for an experiment are assigned randomly to one of several possible values of X, the independent variable. Does not say how the subjects were selected for participation.

random sampling

how researchers select people for participation in a study- they are selected at random.

external validity

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

sample of convenience

subjects included in an investigation that appear to be selected merely because that are available, whether of not they are of optimal suitability to test the hypothesis

replication

implementation of the same procedures repeatedly in identical form to see if the relationships hold in a consistent fashion

observational study

research design in which the researcher does not have control over values of the independent variable, which occurs naturally.

cross-sectional observational studies

studies focusing on variation between spatial units for a single time unit

time-series observational studies

studies focusing on variation within a single spatial unit over multiple time units

spatial unit

unit of measurement, usually the subject, ie country, people

time unit

a unit for measuring time periods

data set dimensions

spatial and time units that define data sets

data points

individual measurements or numbers in a set of data