Why do events occur under some conditions and not under others? Research methods that answer
such questions are called causal methods. Ex-post facto research designs – where a researcher
interviews respondents or observers what is or what has been - also have the potential for
discovering causality.
Experiments are studies involving intervention by the researcher beyond that required for
measurement. The usual intervention is to manipulate a variable in a setting and observe how it
affects the subjects being studied. The researcher manipulates the independent or explanatory
variable and then observes whether the hypothesized dependent variable is affected by the
intervention. An example of such an intervention is the study of bystanders and thieves. The major
hypothesis concerned whether people observing a theft would be more likely to report it if they
observed the crime alone or if they were in the company of someone else.
There is at least one independent variable (IV) and one dependent variable (DV) in a causal
relationship. We hypothesize that in some way the IV ‘causes’ the DV to occur.
Agreement between IV and DV;
Time to order of occurrence;
No influence of other variables;
Advantages
A control group serves as a comparison to assess the existence and potency of the
manipulation and pre- and post-test measurements allow checking that the manipulation
occurred before the outcome.
The second advantage of the experiment is that contamination from extraneous variables
can be controlled more effectively than in other designs. This helps the researcher isolate
experimental variables and evaluate their impact over time.
Third, the convenience and cost of experimentation are often superior to other methods.
These benefits allow the experimenter opportunistic scheduling of data collection and the
flexibility to adjust variables and conditions that evoke extremes not observed under routine
circumstances.
Fourth, replication (repeating an experiment with different subject groups and conditions)
leads to the discovery of an average effect of the independent variable across people,
situations and times.
Finally, researchers can use naturally occurring events and, to some extent, field
experiments to reduce subjects perceptions of the researcher as a source of intervention or
deviation in their everyday lives.
Disadvantages
The artificiality(onnatuurlijkheid) of the laboratory is arguably the primary disadvantage of the
experimental method. Second, generalization from non-probability samples can pose problems
despite random assignment: the extent to which a study can be generalized, say, from college
students to managers or executives is open to question.
Third, the number of variables one can include in an experiment is much more limited than, for
example, in survey research.
There are seven activities the researcher must accomplish in order to make the endeavour (streven)
successful:
1. Selecting relevant variables;
2. Specifying the level of treatment;
3. Controlling the experimental environment;
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