Experimental Design (2)

Transcription

1 Experimental Design (2) Kerry Kilborn Department of Psychology

2 Overview Basic and applied psychology Generation of research ideas Hypotheses and operational definition Choosing a research design

3 Creating Change Basic Research Applied Research

4 Basic Research Basic research questions Theory-driven Examples Perception, memory, thinking, language, learning, motivation, and emotion Social behaviour Development and individual differences Biological correlates of behaviour

5 Applied Research Determined by practical problems Problem solving and less explanation Examples: psychodiagnostics (assessing personality, reviews...) work psychology (work environment, software design...) Organisational Psychology (Staff Management...) Abnormal Psychology (diagnosis, therapy...)

6 Why basic research? Focus on practical problems might lead to neglect of important research areas Accumulation of knowledge Basic research attempts to provide theories that can be practically applied Nothing is as practical as a sound theory

7 Let s do some research! Develop a question Generate a hypothesis Form operational definitions Choose a research design Consider ethics Collect data Analyse data and form conclusions Report research results

8 Generation of Research Ideas Personal experiences (e.g., developmental stages - Piaget) Psychological literature Inconsistencies in or problems with previous research

9 Where to find information Scientific journals: Psychological Review Psychological Bulletin Journal of Personality and Social Psychology Journal of Abnormal Psychology Quarterly Journal of Experimental Psychology Journal of Applied Psychology British Journal of Psychology Social Science Citation Index (SSCI) Online search: PsycLIT (1887-today!)

10 Example: PsycLIT-Search search word: Anorexia. Search result: 5461 entries ITLE Metabolic changes in the brain of patients with anorexia and bulimia nervosa as detected by proton magnetic resonance spectroscopy. UTHOR Roser,-Werner; Bubl,-Reinhard; Buergin,-Dieter; Seelig,-Joachim; Radue,-Ernst-W.; Rost,-Barbara OURCE International-Journal-of-Eating-Disorders.1999 Sep; Vol 26(2): UBLICATION YEAR 1999 BSTRACT Examined metabolic alterations in the brains of 20 patients (mean age 19 yrs) with anorexia and bulimia nervosa, using localized proton magnetic resonance spectroscopy (-sup-1h-mrs). Age and sex-matched healthy Ss served as controls. -sup-1h-mrs revealed metabolic changes, such as a significant decrease of both myoinositol and lipid compounds within the frontal white matter. The concentration of these compounds was further reduced with... ((c) 1999 APA/PsycINFO, all rights reserved).

11 Hypotheses and Variables Hypotheses usually contain a statement about the relationship of two variables Frustration causes aggression Attending Experimental Design increases critical thinking skills by 50 % All humans are subject to qualitatively different sleep phases

12 How are hypotheses generated? curious observations, e.g., moon illusion scientific controversies and theories, e.g., multi-store theory of memory practical problems, e.g., is it better to learn in a mode that is either massive or distributed?

13 Variables Researchers measure variables (e.g., anxiety) but also manipulate variables (stressful situation) Two types of variables Manipulated (Independent) Variables Measured (Dependent) Variables

14 Research Question (Expected Answer) Hypothesis Testable Prediction Empirical Study Results (Data) Are results consistent with predictions? Yes Hypothesis is confirmed No Hypothesis is disconfirmed No Problems with Methods? Yes Improve method and conduct new study Rectify or modify hypothesis

15 Verification and Falsification Verification Empirical confirmation of a hypothesis (weaker than proving a statement) Falsification Rejection of a hypothesis on the basis of empirical evidence (weaker than disproving a statement)

16 Samples People we are going to study. Taken as a small subset but assumed to be representative of the population, i.e., selected from a population Population = All existing members of a group (e.g. undergraduate students). Aim To generalise from a sample to the population. Problem Is it justified to generalise from a sample to a vast number of people?

17 Statistical Hypotheses Hypothesis: There are more Yellows than Greens Population Samples

18 Types of Hypotheses Universal Hypotheses Statement x holds true for all elements of a given environment (all people die ) Existence Hypothesis Statement x holds true at least for one element of a given environment (there is life on mars ) Statistical Hypothesis Statement x is probable to hold true (frustration causes aggression in 85% of the cases )

19 Empirical Tests of Hypotheses Universal Hypothesis Existence Hypothesis Statistical Hypothesis Verification No Yes (organisms on mars) Falsification Yes (all swans are white ) No No No

20 Hypotheses and Variables Hypotheses usually contain a statement about the relationship of two variables Frustration causes aggression Attending Experimental Design increases critical thinking skills by 50 % All humans are subject to qualitatively different sleep phases

21 Variables Researchers measure variables (e.g., anxiety) but also manipulate variables (stressful situation) Two types of variables Manipulated (Independent) Variables Measured (Dependent) Variables

22 Choosing a research design Observational and correlational designs Measure variables through observation or surveys to predict behaviour Experimental designs Manipulate an independent variable and measure a dependent variable with setting under control of researcher Quasi-experimental and single-case designs If control over important variables is not possible (e.g., critical thinking skills in students ) Examine an individual to describe, predict, or understand (treat) the behaviour of one individual

23 Samples People we are going to study. Taken as a small subset but assumed to be representative of the population, i.e., selected from a population Population = All existing members of a group (e.g. undergraduate students). Aim To generalize from a sample to the population. Problem Is it justified to generalise from a sample to a vast number of people?

24 Statistical Analysis