PS: Introduction to Psycholinguistics Winter Term 2005/06 Instructor: Daniel Wiechmann Office hours: Mon 2-3 pm Phone: Web:

Evaluating the results: Just a theory? Def. ‘theory’:  A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.

Evaluating the results: The scientific hypothesis Def: ‘hypothesis’ A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation. Universal quantification (All X are Y) (implicit) formal structure of conditional (potentially) falsifiable

Evaluating the results: types of variables  Def: ‘variable’  A symbol that can assume a set of values (for sets > 1) Compare: ‘constants’ have a fixed value

Evaluating the results: types of variables: A  C  Independent variable Occurs in antecedent of conditional (‚If‘-part) Used to decribe object of investigation  Dependent variable Occurs in consequence of conditional (‚then‘- part) Its distribution/variation is to be explained by independent variable‘s

Evaluating the results: types of variables  We need to formulate two hypothesis Our claim under investigation: alternative hypothesis (H1) The hypothesis we will accept in the absence of evidence for our hypothesis: null hypothesis (H0) (H0 is always logically complementary to H1)

Evaluating the results: Example: Particle placement  Peter picked up NP [the book].  Peter picked NP [the book] up. Question: When do speakers use which construction?

Evaluating the results: Example: Particle placement H1: The placement of the particle is contingent on the ‘heaviness’/length of respective NP H0: The placement of the particle is NOT contingent on the ‘heaviness’/length of respective NP

Evaluating the results: Example  Transform H1 (and H0) into conditionals If the respective postverbal NP is heavy, then the particle will precede it. The heavier the postverbal NP, the more likely it is that the particle precedes it.

Important concepts  Probability of error (p) Empirical science is all about finding evidence against H0 (‘principle of falsification’; cf. Popper 1964) We generalize from samples to populations p expresses the likelihood that the observed result occurs, if H0 holds true if p < 0.05 (level of significance), H1 will be assumed