EXPERIMENTAL DESIGNS

Chapter 7

Anggota Kelompok:

Kiki Rizky Amalia (14080574068)Anjis Fauziah (14080574074)Cindhy Audina B. (14080574075)Syantia Olivia N. (14080574078)Hanum Aula R. (14080574104)Diyah Aprilia (14080574169)Melia Dwi R. (14080574214)

THE LAB EXPERIMENT

As stated earlier, when a cause-and-effect relationship between an independent and a dependent variable of interest is to be clearly established, then all other variables that might contaminate or confound the relationship have to be tightly controlled.

CONTROL

The manager cannot prove that the special training alone caused greater effectiveness, since the previous intermittent experience of some secretaries with the web is a contaminating factor. If the true effect of the train- ing on learning is to be assessed, then the learners‘ previous experience has to be controlled.

MANIPULATION OF THE INDEPENDENT VARIABLE

certain manipulations need to be tried. Manipulation simply means that we create different levels of the independent variable to assess the impact on the dependent variable

CONTROLLING THE CONTAMINATING EXOGENOUS OR “NUISANCE” VARIABLES

• Matching Groups • Randomization

CONTROLLING THE CONTAMINATING EXOGENOUS OR “NUISANCE” VARIABLES

Matching Groups One way of controlling

the contaminating or ―nuisance‖ variables is to

match the various groups by picking the confounding

characteristics and deliberately

spreading them across groups.

RandomizationAnother way of controlling the

contaminating variables is to assign the 60 mem- bers randomly (i.e., with no predetermination) to the four groups. That is, every member would have a known and equal chance of being assigned to any of these four groups

Advantages of Randomization that in the former

case individuals are deliberately and consciously matched to control the differences among group members,

INTERNAL VALIDITY

• Internal validity refers to the confidence we place in the cause-and-effect relationship in research with high internal validity, we are relatively better able to argue that the relationship is causal, whereas in studies with low internal validity, causality can- not be inferred at all.

EXTERNAL VALIDITY OR GENERALIZABILITY OF LAB EXPERIMENTS

• Representasi the results of the investigation or can the results of the invrstigation in generalitation.

THE FIELD EXPERIMENT

A field experiment, as the name implies, is an experiment done in the natural envi- ronment in which work goes on as usual, but treatments are given to one or more groups

External validity and internal validity

External validity refers to the extent of generalizability of the results of a causal study to other settings, people, or events

Internal valid-ity refers to the degree of our confidence in the causal effects (i.e., that variable X causes variable Y)

TRADE-OFF BETWEEN INTERNAL AND EXTERNAL VALIDITY

•There is thus a trade-off between internal validity and external validity. If we want high internal validity, we should be willing to settle for lower external validity and vice versa. These problems of external validity usually limit the use of lab experiments in the management area. Field experiments are also infre- quently undertaken because of the resultant unintended consequences—person- nel becoming suspicious, rivalries and jealousies being created among departments, and the like.

FACTORS AFFECTING INTERNAL VALIDITY

• History Effects • Maturation Effects • Testing Effects • Instrumentation Effects • Selection Bias Effects • Statistical Regression • Mortality

History Effects

Certain events or factors that would have an impact on the independent variable dependent variable relationship might unexpectedly occur while the experimentis in progress, and this history of events would confound the cause and effect relationship between the two variables, thus affecting the internal validity.

Maturation Effects

The maturation effects are a function of the processes both biological and psychological operating within the

respondents as a result of the passage of time.

Testing Effects

• Frequently, to test the effects of a treatment, subjects are given what is called a pr etest (say, a short questionnaire eliciting their feelings and attitudes). That is, first a measure of the dependent variable is taken (the pretest), then the treatment given, and after that a second test, called the posttest, administered.

Instrumentation Effects

• Instrumentation effects 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 Effects

• The threat to internal validity could also come from improper or unmatched selection of subjects for the experimental and control groups.

Statistical Regression

• The effects of statistical regression are brought about when the members 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 the members in the experimental or control group or both, as the experiment progresses.

IDENTIFYING THREATS TO INTERNAL VALIDITY

1) History Effects 2) Maturation. 3) Instrumentation. 4) Selection Bias 5) Statistical Regression 6) Mortality

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.

FACTORS AFFECTING EXTERNAL VALIDITY

external validity raises issues about the generalizability of the findings to other settings.

REVIEW OF FACTORS AFFECTING INTERNAL AND EXTERNAL VALIDITY

In summary, at least seven contaminating factors exist that might affect the internal validity of experimental designs. Threats to external validity can be combated by creating experimental conditions that are as close as possible to the situations to which the results of the experiment are to be generalized.

TYPES OF EXPERIMENTAL DESIGNS AND INTERNAL VALIDITY

• Quasi-Experimental Designs • True Experimental Designs • Solomon Four-Group Design and Threats to Internal Validity • Double-Blind Studies • Ex post facto designs

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.

ETHICAL ISSUES IN EXPERIMENTAL DESIGN RESEARCH

The last item is somewhat controversial as to whether or not it should be an ethical dilemma, especially in organizational research.

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