Lecture_02.md

Lecture #2

Defining Science

Asking and answering verifiable questions

observation (data) = pattern

hypothesis = mechanism to explain pattern

mechanism based on natural phenomena

repeatable (observations, and methods)

falsifiable (mechanism can be rejected with additional data)

parsimony (simple explanations favored over complex ones) Occam’s razor

“confirmation” from independent sources

concilience - consistency with other established observations and mechanisms

“belief” in mechanism based on empirical evidence + scientific method

evidence changes -> belief changes

Deduction & Induction

deduction going from general to specific

syllogism from Aristotle

Major premise “All flamingoes are pink”

Minor premise “This bird is a flamingo”

Conclusion “This bird is pink

induction going from specific to general

These birds are flamingoes

All of these birds are pink

All (or most) flamingoes are pink

• note that scientists infer but data implies*

• *data is a plural noun: “these data are ambiguous”, singular form is datum

Inductive Method (Bacon)

• Bacon 17th century politician, writer, philosopher, “real” Shakespeare
• Novus Organum 1620 break from orthodoxy in education
• begin with simple observation and hypothesis
• derive and test new predictions
• modify and retest
• continue cycle until confirmatio reached

Paradigm (Kuhn)

• 1973 “Structure of Scientific Revolutions”

paradigm: a view of nature that implicitly defines legitimate questions and problems

synthetic

open-ended

defines domain for research

• paradigm is more than a single hypothesis
• Darwin’s theory of natural selection, Einstein’s relativitiy, Freud’s theory of psychoanalysis
• implicit rules of solving a jigsaw puzzle
• story of psychology test with red and black cards
• like political revolution, carried out by young & resisted by old

Hypothetico-Deductive Method (Popper)

• The Logic of Scientific Discovery (1950)
• arch enemy of Kuhn
• progressive/optimistic versus relativistic/pessimistic Kuhn

Inductive vs. Hypothetico-Deductive Method

Inductive Method	Hypothetic-Deductive Method
confirmation of hypothesis	refutation of hypotheses
initial hypothesis repeatedly modified	multiple hypotheses tested and discarded
progress through accumulation	progress through elimination
consensus	controversy

Inductive Method Flaws

• does not consider multiple alternatives
• more than 1 hypothesis can account for outcome
• may never reach “correct” hypothesis from repeated modification

H-D Flaws

• hypothesis list must include “correct” mechanism
• hypotheses may not be mutually exclusive
• when should hypothesis be definitively discarded?

Null Hypothesis

null hypothesis - no “biological mechanism” other than sampling error or other sources of unspecified variation

• dichotomy between H0 and NOT H0
• statistics used to test for pattern, but we must make explicit inference to arrive at mechanism