Part 4: Experiments Flashcards
Observation:
Registering an empirical phenomenon.
Manipulation:
Changing a factor in a study.
Intervention:
Changing an independent variable.
Control:
Reducing the influence of disturbing factors from influencing the outcome.
Independent variables:
Variables that are hypothesised to affect the dependent variable.
Dependent variables:
The variable that changes depending on the changes to the independent variable.
Experiment:
An observational process characterized by control of the background factors (often through manipulation), intervention on the real target variable through manipulation and observation of the difference caused by this intervention.
Method of difference:
By creating two identical groups, and making an intervention on only one of them, the causal effect of that intervention can be studied, since the intervention is the only factor different between the groups.
Control group:
A contrast class that is not subjected to the intervention, but is similar to the treatment group in all other relevant aspects.
Treatment group:
A class that is subjected to the intervention.
Observational study:
An observational process characterized by control of the background factors and observation of an outcome, lacking an intervention.
Natural experiment:
An observational study where circumstances are organized as if there had been manipulation for intervention and control but no manipulation is in fact done.
Field experiment:
An experiment where there is manipulation for intervention, but where several background variables are not controlled, in particular not controlled through manipulation.
Laboratory experiment:
An experiment where there is manipulation for intervention and where all or most relevant variables are controlled.
Simulation experiment:
A model study where the model is created as to mimic an experiment, but where the variable that is intervened on is only represented, rather than actually present.
Internal validity:
An inference about an experimental system is internally valid, if the relation between intervention and observed effect inferred from the experiments is indeed true and is not confounded by uncontrolled background factors.
Observer effect / influence problem:
The act of observation changes what is observed.
Confirmation bias / interpretation problem:
The observation is registered incorrectly due to psychological properties of the observer.
Placebo effect:
The therapeutic effect that an inert substance or treatment, designed to have no therapeutic value, has on a patient
Selection bias:
A factor influences the selection of the sample, or the division in to test and control group, which one did not aim to create.
Repetition:
Performing a study again, exactly following the description of the original study.
Reproduction:
Repeating a study and obtaining the same result as in the original study.
Replication:
Performing a variation of a study with the intention to achieve the same result, where some aspect of the study has been changed to learn how this aspect influenced the result.
Constancy:
Holding background factors constant between test and control group or between trials in a study.
Elimination:
Removing the influence of a background factor
Blinding:
Eliminating observer effect or the influence problem through limiting information about the study to participants or observers.
Single blinding / subject blinding:
Blinding the participants in a study, for instance about whether they are in the test or control group.
Experimenter blinding:
Blinding the observers in a study, for instance about which subjects are in the test and control group.
Double blinding:
A study is double blind if both subject blinding and experimenter blinding are implemented
Separation:
Registering the effect of a background variable.
Randomization:
Using a random process to divide into test and control, for instance by flipping a coin.
Random sampling:
Using a random process to collect a sample from the population. Not to be confused with randomization.
Evidential hierarchies:
A ranking of types of evidence based on the processes that produced this evidence.
Data stratification:
Dividing a sample into categories based on specific properties before randomizing, thus ensuring that these properties are correctly represented in the test and control groups, for instance mirroring their distribution in the population.
Known factor:
A factor which you are aware of constitutes a relevant background factor.
Unknown factor:
A factor which is a relevant background factor, but which you are unaware of.
External validity:
An inference from an experimental system to a different target of interest is externally valid, if the conclusion holds not only for the system but also for the target, for instance an inference from a sample to a population.
