Framing an Experimental Hypothesis WP5 Professor Alan K. Outram University of Exeter 8 th October 2012.

Framing an Experimental Hypothesis

WP5

Professor Alan K. Outram

University of Exeter

8th October 2012

Science vs. Art…

the term science is extended to denote a department of practical work which depends on the knowledge and conscious application of principles;

an art, on the other hand, being understood to require merely knowledge of traditional rules and skill acquired by habit.

Empiricism

• Empirical:– 3. In matters of art or practice: That is guided by

mere experience, without scientific knowledge; also of methods, expedients, etc.

• Empiricism:– 2. a. The use of empirical methods in any art or

science. b. Philos. The doctrine which regards experience as the only source of knowledge.

(definitions from OED)

Induction

• 6. The bringing forward, adducing, or enumerating of a number of separate facts, particulars, etc., esp. for the purpose of proving a general statement.

Strong Induction

All observed crows are black

Therefore:

All crows are black

Weak Induction

Many speeding tickets are given to teenagers

Therefore:

All teenagers drive too fast

Induction is Probabilistic

As evidence accumulates, the degree to which it comes to support a hypothesis, should tend to indicate that false hypotheses are probably false and true ones are probably true.

Deduction

• Premises logically entail the conclusion• The truth of the premises provide a guarantee

of truth to the conclusion.

Deduction example 1

All animals are mortal.All humans are animal.

Therefore:

All humans are mortal.

Deduction example 2

All apples are fruit.All fruits grow on trees.

Therefore:

All apples grow on trees.

Hypothetico-Deductive reasoning

Experiment• 1. a. The action of trying anything, or putting it

to proof; a test, trial • 3. An action or operation undertaken in order

to discover something unknown, to test a hypothesis, or establish or illustrate some known truth. a. in science.

“All knowledge is provisional, conjectural and hypothetical”

Falsification

• Theories (hypotheses) must be tested against empirical knowledge, through experimentation.

• Theories are not held to be true (verified) if they pass such tests, they merely remain valid until falsified or superseded

• Exceptions do not prove the rule, they falsify it!

Framing Good Experimental Hypotheses

• Prioritise hypotheses that are not trivial, particularly those premises which have wide relevance and scope.

• Is the hypothesis testable (i.e. is it possible to falsify it, both in theory and practice)?

• Keep the hypothesis simple: often best to test one thing at a time. For more complex questions, test multiple, simple hypotheses.