Question

Situation #1: you want to look at a variable that you cannot manipulate

Situation #2: there are ethical needs that require quasi-designs

For each situation, tell me why a quasi-experimental design is needed given that situation. Describe a brief research study for each to justify a quasi-experimental (rather than experimental) design

Answer 1

Quasi-experimental research designs are experimental designs that do not provide for full control of extraneous variables primarily because of the lack of random assignment to groups.

You could say that they are kind of “in-between” designs; they are not great, but they are not too bad either. Because they are classified as a type of experimental research, the independent variable must be manipulated (although real-world events that are highly similar to experimenter manipulation also may be appropriate for quasi-experimental research). Quasi-experimental research involves the manipulation of an independent variable without the random assignment of participants to conditions or orders of conditions.

As we know that the key components of the experimental design are the manipulation of variables and ethical issues. If these conditions are not likely to satisfy then we need a quasi-experimental design.

1) Manipulation:

One potential threat to internal validity (how accurate is our results) in experiments occurs when participants either drop out of the study or refuse to participate in the study. If particular types of individuals drop out or refuse to participate more often than individuals with other characteristics, this is called differential attrition. For example, suppose an experiment was conducted to assess the effects of a new reading curriculum. If the new curriculum was so tough that many of the slowest readers dropped out of school, the school with the new curriculum would experience an increase in the average reading scores. The reason they experienced an increase in reading scores, however, is because the worst readers left the school, not because the new curriculum improved students' reading skills.

It is always possible to manipulate the variables rather sometimes the event has taken place already then we need a Quasi-experimental study. Quasi-experimental methods that involve the creation of a comparison group are most often used when it is not possible to randomize individuals or groups to treatment and control groups. This is always the case for ex-post impact evaluation designs. It may also be necessary to use quasi-experimental designs for ex-ante impact evaluations, for example, where ethical, political or logistical constraints, like the need for a phased geographical roll-out, rule out randomization.

2) Ethical Issues:

It is particularly important in experimental research to follow ethical guidelines. Protecting the health and safety of research subjects is imperative. In order to assure subject safety, all researchers should have their project reviewed by the Institutional Review Boards (IRBS).

The basic ethical principles:

• Respect for persons -- requires that research subjects are not coerced into participating in a study and requires the protection of research subjects who have diminished autonomy
• Beneficence -- requires that experiments do not harm research subjects and that researchers minimize the risks for subjects while maximizing the benefits for them
• Justice -- requires that all forms of differential treatment among research subjects be justified

Another example of ethical issues can be-

if we study the effect of maternal alcohol use when the mother is pregnant, we know that alcohol does harm embryos. A strict experimental design would include that mothers were randomly assigned to drink alcohol. This would be highly illegal because of the possible harm the study might do to the embryos.