Research methods for business

Fourth Edition Chapter 7 EXPERIMENTAL DESIGNS

MANIPULATION OF THE INDEPENDENT VARIABLE

Manipulation simply means that we create different level of the independent variable to asses the impact on the dependent variable

CONTROLING THE CONTAMINATING EXOGENOUS OR “ NUISANCE “ VARIABLES

Matching group one way of controlling the contaminating or “ nuisance “ variables is to match the various group by picking the confounding characteristic and deliberately spreading them across group

Randomization Another way controlling the contaminating variables is to assign the 60 members randomly ( i.e., with no predetermination ) the four groups . That is , every member would have a known and equal chance of being to any of these four group .

Advantage of randomization The difference between matching and randomization is that in the former case individual are deliberately and consciously matched to control the differences among group members , whereas in the later case we expect that the process of randomization would distribute the inequalities among the group based on the jaws of normal distribution . Thus we need not be particularly concerned about any known or unknown confounding factor .

INTERNAL VALIDITY

internal validity refers to the confidence we place in the cause – and – effect relation-ship .

EXTERNAL VALIDITY OR GENERALIZABILITY OF LAB EXPEREIMENTS

The field experiment a field experiment , as the name implies , is an experiment done in the natural environment in which work goes on as usual , but treatment are given to one or more groups .

External validity , external validity refers to the extent of generalizability of the result of a casual study to other setting , people , or events and internal validity refers to degree of our confidence in the causal effect ( i.e., that variable X causes variable Y )

FACTOR AFFECTING INTERNAL VALIDITY

Even the best designed lab studies could be influenced by factor that might affect the internal validity of the lab experiment

These possible confounding factor pose a threat to internal validity .

History Effects certain events or factors that would have an impact on the independent variable – dependent variable relationship might unexpectedly occur while the experiment is progress , and this history of events would confound the cause – and – effect relationship between the two variables , thus affecting the internal validity

Maturation Effect cause – and – effect inferences can also be contaminated by the effect of the passage of time – another uncontrollable variable .

Testing Effect frequently , to test the effect of a treatment , subject are given what is called a pretest ( say , a short questionnaire eliciting their feeling and attitudes ) . That is , and first a measure of the dependent variable is taken ( pretest ) , then the treatment given , and after that a second test , called the postest

Instrument Effects instrumentation effect are yet another source of threat to internal validity . These might arise because of a change in the measuring instrument between pretest and posttest , and not because of the treatment’s differential impact at the end ( cook & Campbell , 1979a

Selection Bias Effect the threat to internal validity could also come from improper or unmatched selection of subject for experimental and control groups

Statistical regression the effect of statiscial regression are brought about when chosen for the experimental group have extreme scores on the dependent variable to begin with

Mortality another confounding factor on the cause- and – effect relationship is the mortality or attrition of members in the experimental or control group or both , as the experiment progresses .

IDENTIFYING THREATS TO INTERNAL VALIDITY

History effects the action of the two members in the participative group by way of unexpectedly moving around in an exited manner and remarking that participative leadership is great and the performance is bound to high in this group might have boosted the morale of all the members in the group .

Maturation it is doubtful that maturation will have any effect on morale in this situation

Testing the pretest are likely to have sensitized the respondents to the posttest

Instrumentation since the same questionnaire has measured morale both before and after the treatment for all members , we do not expect instrumentation bias

Selection bias since members have been randomly assigned to all group , we do not expect selection bias to exist

Statistical Regression though not specifically stated , we can assume that all the member participacing in the experiment were selected randomly from a normally distributed population

Mortality since members dropped out of two experimental group , the effectts of morality could affect internal validity

INTERNAL VALIDITY IN CASE STUDIES

If there are several threats to internal validity even in a tightly controlled lab experiment, it should become quite clear why we cannot draw conclusions about causal relationships from case studies that describe the events that occurred during a particular time.

FACTOR AFFECTING EXTERNAL VALIDITY

Whereas internal validity raises questions about whether it is the treatment alone or some additional extraneous factor that causes the effect , external validity raises issues about the generalizability of findings to other setting .

TYPES OF EXPERIMENTAL DESIGNS AND INTERNAL VALIDITY Quasi-experimental Designs Pretest and posttest Experimental group

design Posttests only whit Experimental and

control groups

True experimental designs

Experimental designs , which include both the treatment and control groups and record information both before and after the experimental group is exposed to the treatment , are known as exposed to the pretest and post test

The design can be visual depicted as figure 7.5 . Two groups one experimental and the other control are both exposed the pretest and post test .

Solomon four – Group Design to gain more confidence in internal validity in experimental designs , it is advisable to set up two experimental groups and two control groups for the experiment.one experimental group and one control group can be given both the pretest and postest , as shown in figure 7.6

Double – blind studies

When extreme care and rigor are needed in experimental designs as in the case of discovery of new medicines that could impact on human lives, blind studies are conducted to avoid any bias that might creep in.

Ex Post Facto design

Cause-and-effect relationships are sometimes established through what is called the ex post facto design. Here, there is no manipulation of the independent variable in the lab or field setting, but subjects who have already been exposed to a stimulus and those not so exposed are studied.

SIMULATION

An alternative to lab and field experimentation currently being used in business research is simulation. Simulation uses a model-building technique to determine the effects of changes, and computer-based simulations are becoming popular in business research.

A simulation can be thought of as an experiment conducted in a specially created setting that very closely represents the natural environment in which activities are usually carried on. In that sense, the simulation lies somewhere between a lab and a field experiment, insofar as the environment is artificially created but not far different from ―reality.‖ Participants are exposed to real-world experiences over a period of time, lasting anywhere from several hours to several weeks, and they can be randomly assigned to different treatment groups.

ETHICAL ISSUES IN EXPERIMENTAL DESIGN RESEARCH

The following practices are considered unethical: • Putting pressure on individuals to participate in experiments through coercion, or applying social pressure. • Giving menial tasks and asking demeaning questions that diminish their selfrespect. • Deceiving subjects by deliberately misleading them as to the true purpose of the research. • Exposing participants to physical or mental stress. • Not allowing subjects to withdraw from the research when they want to. • Using the research results to disadvantage the participants, or for purposes not to their liking. • Not explaining the procedures to be followed in the experiment. • Exposing respondents to hazardous and unsafe environments as we saw earlier in the case of Johns Hopkins University. • Not debriefing participants fully and accurately after the experiment is over. • Not preserving the privacy and confidentiality of the information given by the participants. • Withholding benefits from control groups.

MANAGERIAL IMPLICATIONS

Before using experimental designs in research studies, it is essential to consider whether they are necessary at all, and if so, at what level of sophistication. This is because experimental designs call for special efforts and varying degrees of interference with the natural flow of activities.

Some questions that need to be addressed in making these decisions, are the following:

1. Is it really necessary to identify causal relationships, or would it suffice if the correlates that account for the variance in the dependent variable were known? 2. If it is important to trace the causal relationships, which of the two, internal validity or external validity, is needed more, or are both needed? If only internal validity is important, a carefully designed lab experiment would be the answer; if generalizability is the more important criterion, then a field experiment would be called for; if both are equally important, then a lab study should be first undertaken, followed by a field experiment, if the results of the former warrant the latter. 3. Is cost an important factor in the study? If so, would a less rather than more sophisticated experimental design do?

FURTHER EXPERMENTAL DESIGNS

It would be useful to understand some terms before describing the various designs.

The term factor is used to denote an independent variable—for example, price.

The term level is used to denote various gradations of the factor—for example, high price, medium price, low price—while making it clear as to what these gradations signify (e.g., high price is anything over $2 per piece; medium is $1–$2 per piece; low price is anything less than $1 per piece).

Treatment refers to the various levels of the factors A blocking factor is a preexisting variable in a given situation that

might have an effect on the dependent variable in addition to the treatment, the impact of which would be important to assess