1 METHODS 1 CH 2 Psychology as a Science In this lecture we will discuss limits of common sense o science a method for understanding o o methods of science description correlation experimentation o evaluating data with statistics o sources of error and bias in research Science vs Common Sense Common sense and intuition often tell us about psychology o e g suppose a study tells us that separation weakens romantic attraction o common sense may tell us out of sight out of mind o or common sense may say the opposite absence makes the heart grow fonder Common sense can be inconsistent and based on hindsight Science helps build explanations that are consistent and predictive rather than conflicting and postdictive hindsight Science is based on o knowledge of facts o developing theories o testing hypotheses o public and repeatable procedures Scientific Inquiry Facts are what need to be explained o objective viewable by others o based on direct observation o reasonable observers agree are true Theory is a set of ideas that o explains facts o makes predictions about new facts Hypothesis o prediction about new facts o can be verified or falsified What do we learn from Clever Hans story o Value of skepticism o Value of careful observations under controlled conditions o Problem of observer expectancy effects Methods in Psychology 2 Setting field vs laboratory Methods of data collection o self report vs observational Research plan or design o descriptive o correlational o experimental Descriptive Study Describes a set of facts Does not look for relationships between facts Does not predict what may influence the facts May or may not include numerical data Example measure the of new students from out of state each year since 1980 Correlational Study Collects a set of facts organized into two or more categories or variables o measure parents disciplinary style o measure children s behavior Correlation reveals relationships among facts o e g more authoritative parents have children who behave better o Relationships found in one sample can be used to infer predictive relationships in other o Correlations specify two aspects of relationships measured by the correlation samples coefficient r o Type of Relationship o Strength of Relationship Positive Correlation a relationship in which the values of one variable tend to increase decrease as the values of other variable increase decrease Negative or Inverse Correlation a relationship in which the values of one variable tend to increase decrease as the values of other variable decrease increase r 1 00 Perfect positive correlation strongest possible positive correlation no error of prediction r 1 00 Perfect negative correlation strongest possible negative correlation no error of prediction r 0 00 No correlation and obviously the weakest possible correlation virtually guaranteed error of prediction Correlation cannot prove causation o Do authoritative parents produce better behaved children o Do better behaved children encourage parents to be authoritative May be an unmeasured common factor o e g good neighborhoods produce authoritative adults and well behaved children Experiments 3 Direct way to test a hypothesis about a cause effect relationship between variables One variable is controlled by the experimenter the independent variable o e g authoritative vs authoritarian classroom The other is observed and measured the dependent variable o e g cooperative behavior among students Independent variable the controlled factor in an experiment o o hypothesized to cause an effect on another variable Dependent variable the measured facts o o hypothesized to be affected Independent Variable o Must have at least two levels categories male vs female numeric ages 10 12 14 o Simplest is experimental vs control experimental gets treatment control does not Operational Definition o An operation definition specifies the operations used to measure a variable Operationally define Chocolate Cake Operationally define Handedness Experimental Design o Levels may differ between or within people o Within subject experiment different levels of the independent variable are applied to o Between groups experiment different levels of the independent variable are applied to the same subject different groups of subjects o Random sample every member of the population being studied should have an equal chance of being selected for the study o Random assignment every subject in the study should have an equal chance of being placed in either the experimental or control group o Randomization helps avoid false results o How would we assess the following hypothesis Anxiety increases the desire to affiliate What is the independent variable IV o Operationally define it What is the dependent variable DV o Operationally define it What is the hypothesized relationship between the IV and DV 4 Experiments Experimental Design Continued o Stanley Schachter s 1959 Solution Manipulation of the IV Experimental Group Shocks will be extremely painful High Anxiety Control Group Shocks will be mild and painless Low Anxiety Group Group Measurement of the DV Have subjects respond to the following scale after being presented with the conditions i e painful vs mild shock they are expected to endure o o o o o I very much prefer being alone I prefer being alone I don t care very much I prefer being together with others I very much prefer being with others Results Schachter 1959 Wanted to Wait with Others Didn t Care Wanted to Wait Alone Group Total N 20 10 30 62 5 33 3 48 4 N 9 18 27 28 1 60 0 43 5 High Anxiety Low Anxiety Response Total Adapted from Schachter S 1959 The psychology of affiliation Experimental studies of the sources of gregariousness Stanford CA Stanford University Press 9 4 6 7 8 1 N 3 2 5 N 32 30 62 How likely is it that these results are due to chance alone Conventionally it is generally agreed that if the pattern of results are such that it would occur less than five percent of the time given a null or chance pattern then it is considered to be unlikely that the results are due to chance A test of proportions suggests that people experiencing higher levels of anxiety are significantly more likely to want to be together with other people Fisher s Exact p 0 03 Note Schachter scored his ordinal dependent measure as if it were on an interval scale but his conclusions were essentially the same as what the proportion test shows 5 Research Settings o Laboratory a setting designed for research