An experiment can be seen as a structured method for collecting evidence to test a hypothesis. The process of designing a good experiment involves reducing unknowns and establishing a clear relationship between the hypotheis and any expected results. is there a causal relationship that can be established between the intitial conditions and the result? does the collected data actually support (or refute) the hypothesis? is there enough data to draw a conclusion? are there other factors effecting the outcome?

ref. labcraft pp89~96

on unstructured tinkering and statistical validity…

• https://en.wikipedia.org/wiki/Quasi-experiment
• https://en.wikipedia.org/wiki/Natural_experiment
• https://en.wikipedia.org/wiki/Design_of_experiments
• https://en.wikipedia.org/wiki/Concept_development_and_experimentation
• http://www.dummies.com/how-to/content/designing-experiments-using-the-scientific-method.html

demonstration vs. experiment

• A demonstration is a way to explain a principle by an example. it provides evidence of the the principle under investigation.
• An experiment is a test performed to discover an unknown or to validate (or refute) a theoretical principle.