Chapter 2: The methods of psychology Slides prepared by Randall E. Osborne, Texas State University-San Marcos, adapted by Dr Mark Forshaw, Staffordshire University, UK 1 Empiricism: How to Know Things 2 Empiricism Ancient Greece dogmatists (develop theories) empiricists (make observations) The Scientific Method - empiricism Three things make people hard to study complexity variability reactivity 3 Observation: Discovering What People Do 4 The Science of Observation Observe what people do John picked up an apple Explain why they do it he is going to eat it he is going to throw it at me Measurement must define what we wish to measure must find a way to detect it 5 The Science of Observation Operational definition define property to measure in concrete terms detect what our definition describes Easy to measure physical properties like distance Not so easy to measure psychological properties like happiness a specific set of muscular contractions? (EMG) 6 The Science of Observation With so many ways to measure things, it is hard to know what is the right way Problems of defining Validity able to draw accurate inferences construct validity predictive validity 7 The Science of Observation With so many ways to measure things, it is hard to know what is the right way Problems of detecting Reliability same result each time? power case method population sample law of large numbers 8 The Science of Observation Averaging frequency distributions Normal distribution symmetrical Descriptive statistics essential information from a frequency distribution central tendency variability 9 The Science of Observation Central tendency modefrequent meanaverage medianmiddle Variability Range Variance Standard deviation 10 The Science of Observation T-test Comparing means of two samples Independent and related versions Compare error variance with variance attributable to the effect under study Degrees of freedom 11 The Science of Observation Bias Demand characteristics Avoiding demand characteristics observing can cause people to change naturalistic observation helps but not always some things do not occur naturally some data require interaction with a person 12 The Science of Observation The blind observer expectations can influence observations expectations can influence reality Double-blind 13 Explanation: Discovering Why People Do What They Do 14 The Science of Explanation Ultimate goal of research is causal Knowing what is not the same as why How are variables related? Is the relationship causal? Correlation variable patterns of variation 15 The Science of Explanation Measurements tell us about properties of objects and events Patterns of variation tell us about relationships between variables Correlations are ways of expressing relationships between variables 16 The Science of Explanation Measuring correlation more-more/less-less more-less/less-more Correlation coefficient measure of direction & strength r = 1 r = -1 r = 0 17 The Science of Explanation Pearson: parametric Spearman: non-parametric Correlation co-efficients Extent to which two variables vary together, or co-vary Hence covariance 18 The Science of Explanation Causation related is not caused To discover causality we need more empiricism Third-variable problem natural correlation (age and number of children borne) variables that are causally related are correlated but not all variables that are correlated are causally related 19 The Science of Explanation Two variables are correlated only three possible relationships X causes Y Y causes X Z causes both X and Y cannot know with correlation which it is 20 The Science of Explanation Third variable correlation third variable problem Matched samples two samples identical on third variable Matched pairs each participant in one sample identical to one other participant in another sample on a third variable 21 The Science of Explanation Experiment 2 critical features (1) Manipulation independent variable control group experimental group dependent variable measured (2) Randomization (controls for 3 rd variable) versus self-selection 22 The Science of Explanation Significance helps determine if random assignment failed calculate odds random assignment failed - differences between control and experimental group likely to be caused by third variable? 23 The Science of Explanation Drawing conclusions Internal validity experiment internally valid when: independent variable manipulated participants randomly assigned dependent variable measured correlation in pattern of variation and variation can be measured in dependent variable 24 The Science of Explanation Drawing conclusions Representative variables external validity theory hypothesis 25 The Science of Explanation Representative samples random sampling Cannot automatically generalise from non-random samples generality doesnt always matter generality can sometimes be determined generality can sometimes be assumed 26 Qualitative Research In depth understanding of experience Thematic Analysis, Grounded Theory, IPA, NA, DA, CA Not theory driven Flexible Researcher as participant Generalization/triangulation 27 The Ethics of Science: First, Do No Harm 28 The Ethics of Science APA code of ethics (1958) BPS Code of Conduct and Ethics (updated in 2006) Informed consent Freedom from coercion Protection from harm Risk-benefit analysis Debriefing 29