Exam 5: Section 2: Experimental and Quasi-Experimental Designs

The central features of the classical experiment are variables, time order, measures, and groups. Like much of the vocabulary of research, the word experiment has acquired both a general and a specialized meaning. According to David Farrington, Lloyd Ohlin, and James Q. Wilson "the defining feature of an experiment lies in the control of the ______ by the experimenter."

The most conventional type of experiment in the natural and the social sciences involves three major pairs of components: 1) independent and dependent variables, 2) pretesting and post-testing, and 3) experimental and control groups. Essentially, an experiment examines the effect of _____.

A control group offsets the effects of the experiment itself. Social scientific experiments seldom involve only the observation of an experimental group, to which a stimulus has been administered. Researchers also observe a _____ to which the experimental stimulus has not been administered.

Experimentation is especially inappropriate for hypothesis testing and evaluation.

The term experiment refers to a specific way of structuring research, usually called the classical experiment.

Randomization plays a significant part in experimental research. Experiments potentially control for many threats to the _____ but researchers must remain aware of these threats. The central features of the classical experiment are independent and dependent variables, pretesting and post-testing, and experimental and control groups created through random assignment.

The problem of threats to internal validity refers to the possibility that conclusions drawn from experimental results may not accurately reflect what went on in the experiment itself. In other words, conclusions about cause and effect may be _____in some systematic way

The experimental design ensures that the cause precedes the effect in time by taking posttest measurements of the dependent variable after introducing the experimental stimulus. The second criterion for causation-an empirical correlation between the cause-and-effect variables-is determined by comparing the pretest in which the experimental stimulus is not present to the posttest for the experimental group after the experimental stimulus is administered. A change in _____ measures demonstrated correlation.

In general, the methods used to select subjects must meet the scientific norm of generalizability. The researcher should be able to generalize from the sample to the population. Additionally, the cardinal rule of subject selection and experimentation is the comparability of the experimental and control groups. For results to be valid it is essential that he experimental and control groups be as _____ as possible.

Variables designated as the independent and dependent variables do not always maintain the same designation. Given the context of the experiment and research question any variable may change its designation. For example alcohol use might serve as an independent variable in one experiment and as _____ in another.

In a general experimental design, subjects are measured on a dependent variable. This is essentially pre-test. Then the subjects are exposed to a stimulus that represents an independent variable, and re-measured on the dependent variable. This is called post-test. Differences noted between the first and second measurements on the dependent variable are then attributed to the influence of the _____.

Experiments are excellent vehicles for the controlled testing of causal processes. Experiments may not be appropriate for evaluation studies.

Most social scientific experiments do not take place in laboratory settings with the exception of psychology in which laboratory experiments are common. Criminal justice experiments are almost always conducted in _____.

A _____ eliminates this possibility because neither the subjects nor the experimenters know which is the experimental group and which is the control. In medical experiments, those researchers who are responsible for administering the drug and for noting improvements are not told which subjects receive the drug

Statistical conclusion validity refers to whether a researcher is able to determine two variables are related. Statistical conclusion validity most often becomes an issue when findings are based on _____ of cases. Because experiments can be costly and time consuming, they are frequently conducted with relatively small numbers of subjects.

Experimental subjects often drop out of an experiment before it is completed, and that can affect statistical comparisons and conclusions. This is termed experimental mortality, also known as _____.

Randomization is the best way to achieve comparability in the experimental and control groups.

Typically the independent variable is the cause and the dependent variable is the effect. The independent variable takes the form of an experimental stimulus that is either present or absent-that is, having two attributes. It is essential that both independent and dependent variables be _____ defined for the purposes of experimentation.