|Experimental design||“A planned interference in the natural order of events.”|
|Subject(s)||Means the subject under study, which can be people, technology and natural phenomena.|
|Sample||Typically you can't study all the individuals of a particular subject pool, so in your experiment you use a sample and hope that the results generalize to the rest of the subjects.|
|Between subjects vs. within subjects design|| Between subjects: Two separate groups of subject/phenomena measured.
Within subjects: Same subjects/phenomena measured twice, on different occasions
|Quasi-Experimental||When conditions do not permit an ideal design to be used and a controlled experiement is impossible, there are other techniques that can be used. These are called quasi-experimental designs.|
|Internal validity||How likely is it that the independent variables caused the dependent variables?|
|External validity||How likely is it that the results generalize to other instances of the phenomenon under study?|
|Correlation||Some factors/variables co-vary when changes in one variable are related with changes in the other, negative or positive.|
|Correlation: Powerful tool||Any variables in the world can be measured for correlation. Only two variables are needed (independent and dependent) for doing correlation studies.|
|Main operating principle behind correlation||There is no causation without correlation.|
|Correlation: Pitfall|| Correlation does not imply causation
between the variables measured!
|Quasi-experimental designs|| Purpose: Where true experimental design is not possible, approximate it.
If direct control over dependent/independent variables is not possible.
|How it works|| 1. One-shot case study (no control group).
2. Single group pre- and post-test (minimal control)
3. ABAB: Single-group repeated measures (slightly less minimal control).
|Limitations||Much greater uncertainty as to the internal and external validity of the quasi-experiments than true experimental designs.|
|What is it?|| A more loose, pre-study using the intended experimental design to tune it.
A pre-study intended to gauge the nature, scales or other factors of the variables to be measured, or the subject to be measured.
|Why and when||Pilots are much more useful than you might think. Yes, it will increase the duration and effort of your experiment BUT: It can significantly improve the quality of the subsequent experiment in many cases. It will certainly clarify and sharpen the experimenter's understanding of one or more of: the experiment, experimental procedure, variables and subjects.|
|Bottom line||Do not try to “save time” by skipping a pilot if a pilot study seems to makes sense.|