Case Assignment: True Experiments

Case Assignment: True Experiments
Case Assignment: True Experiments
Case Assignment: True Experiments
Week 6 assignment 2 Evidence Based Project Proposal For your Dropbox assignment this week, you will write Part 3 of your project proposal. In a one- to two-page paper in APA format, include: Your clinical question How the clinical question indicates the type of study that will be done (quasi-experimental vs. experimental). Describe the type of study. Theoretical framework(s) chosen including a rationale for your choice
EXPERIMENTS AND QUASI-EXPERIMENTS
An experiment is a study in which the researcher manipulates the level of some independent variable and then measures the outcome. Experiments are powerful techniques for evaluating cause-and-effect relationships. Many researchers consider experiments the “gold standard” against which all other research designs should be judged. Experiments are conducted both in the laboratory and in real life situations.
Types of Experimental Design
There are two basic types of research design:
True experiments
Quasi-experiments
The purpose of both is to examine the cause of certain phenomena.
True experiments, in which all the important factors that might affect the phenomena of interest are completely controlled, are the preferred design. Often, however, it is not possible or practical to control all the key factors, so it becomes necessary to implement a quasi-experimental research design.
Similarities between true and quasi-experiments:
Study participants are subjected to some type of treatment or condition
Some outcome of interest is measured
The researchers test whether differences in this outcome are related to the treatment
Differences between true experiments and quasi-experiments:
In a true experiment, participants are randomly assigned to either the treatment or the control group, whereas they are not assigned randomly in a quasi-experiment
In a quasi-experiment, the control and treatment groups differ not only in terms of the experimental treatment they receive, but also in other, often unknown or unknowable, ways. Thus, the researcher must try to statistically control for as many of these differences as possible
Because control is lacking in quasi-experiments, there may be several “rival hypotheses” competing with the experimental manipulation as explanations for observed results
Key Components of Experimental Research Design
The Manipulation of Predictor Variables
In an experiment, the researcher manipulates the factor that is hypothesized to affect the outcome of interest. The factor that is being manipulated is typically referred to as the treatment or intervention. The researcher may manipulate whether research subjects receive a treatment (e.g., antidepressant medicine: yes or no) and the level of treatment (e.g., 50 mg, 75 mg, 100 mg, and 125 mg).
Suppose, for example, a group of researchers was interested in the causes of maternal employment. They might hypothesize that the provision of government-subsidized child care would promote such employment. They could then design an experiment in which some subjects would be provided the option of government-funded child care subsidies and others would not. The researchers might also manipulate the value of the child care subsidies in order to determine if higher subsidy values might result in different levels of maternal employment.
Random Assignment
Study participants are randomly assigned to different treatment groups
All participants have the same chance of being in a given condition
Participants are assigned to either the group that receives the treatment, known as the “experimental group” or “treatment group,” or to the group which does not receive the treatment, referred to as the “control group”
Random assignment neutralizes factors other than the independent and dependent variables, making it possible to directly infer cause and effect