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  2. MAIN TOPICS FOR CLASS  What is an experiment?  What is experimental psychology?  Control and experimental group  Variables in an experiment (IV, DV, Extraneous, control and confounding)  Replication & validity (internal and external) in an experiment
  3.  Experiments have been the mainstay of psychological research for over 150 years  First experimental lab: Leipzig Univ., 1879, Wilhelm Wundt
  4. WHAT IS RESEARCH?  Research is a systematic, logical process for COLLECTING, ANALYZING, INTERPRETING information (DATA) in order to INCREASE our UNDERSTANDING of a given phenomenon.  Research: DISCOVERY & ADVANCEMENT OF HUMAN KNOWLEDGE  What sets research apart from OTHER WAYS OF KNOWING is the SCIENTIFIC APPROACH.
  5.  One method used in psychological research is EXPERIMENTS.  Experiments are very useful when we want to establish CAUSE & EFFECT relationships.  But, what is an experiment? Lets start with an example…..
  6. Lets assume a research question:  What is the effect of instrumental music on learning? Learning what?  A list of words.
  7. STEP 1: SELECT A SAMPLE /SUBJECTS  N=100 students of 2nd year across different courses of LSR So all subjects are:  18-19 years of age  Female  Undergraduate
  8.  Step 2: Randomly divide them into 2 groups  Group 1 N=50 Group 2 N=50 Step 3: Data collection • Each group is given a list of 50 words • 1 hour to learn the list Group 1 N=50 Learns the list with music Group 2 N=50 Learns without music Both groups are asked to recall & write the words They are given 5 minutes for recall.
  9. IMPORTANT FEATURES OF THE DESIGN I was interested in the effect of one thing upon another The groups were randomly created (random selection & random assignment) Groups have to be same/similar in every respect except music The groups were relatively large, as is required for statistical analysis
  10. WHAT WERE THE RESULTS OBTAINED?  Music group performed significant better than non-music group.  What may I conclude?  If the groups were similar in every possible way, except 1 (presence of music)…  Then the difference seen in their performance is most probably due to the factor of music only.
  11. VARIABLE  Any entity that varies and can be measured  Height, weight, income, mileage of a car  In an experiment , a variable may be MANIPULATED, OBSERVED, CONTROLLED
  12. INDEPENDENT VARIABLE Systematically manipulated (altered/varied) by the experimenter to study its effects DEPENDENT VARIABLE The variable which is observed and measured
  13. EXTRANEOUS VARIABLES  Any variable the researcher is not interested in and should be prevented from effecting the outcome of the experiment. Situational Any feature of the research situation which influences the outcome (DV) apart from the IV e.g., NOISE TEMPERATURE TIME OF DAY INDEPENDENT VARIABLE Subject related Characteristics of a subject that may effect the outcome (DV) of the study e.g., INTELLIGENCE MOTIVATION AGE
  14. CONTROL VARIABLES  These are variables kept constant across conditions to minimise their effect on the experiment Examples:  Subjects of both groups come for the experiment at the same time of the day  They study the same list  Time of learning is same for both groups: One hour  All subjects are of the same age, gender
  15. CONFOUNDING VARIABLES  Any extraneous variable that systematically varies with the IV adversely effecting the researcher’s ability to draw CAUSE & EFFECT relations  Confound= Cause confusion
  16. ANOTHER EXAMPLE  AIM: To study the impact of cell phone usage on Driver’s reaction time in an emergency situation  IV?  DV?  Extraneous variables that need to be controlled
  17. IV • Talking on cell phone DV • RT in emergency situations Control • Age of subjects in both groups • Nature of emergency faced by both groups • Driving experience of persons in both groups
  18. WHAT ARE EXPERIMENTS?  Are a method of collecting data…….  Wherein the experimenter creates a situation in which ……….  1 set of variables are manipulated (IV) and another set are controlled (control variables)to……..  Observe a relation of cause and effect between the manipulated variable (IV) and the observed variable (DV) It has 3 elements: • Change in the events that are hypothesized to have an effect – these events are called IV • Looking for the effect of the change on the system of observation- DV • Keeping all other conditions constant- Control variables
  19. CRITERIA FOR AN EXPERIMENT Experiment 1. Manipulation of IV 2. Random assignment of subjects 3. Ability to draw cause and effect relations Quasi-experiment 1. Manipulation of IV 2. NO Random assignment of subjects 3. NO Ability to draw cause and effect relations Ex post facto study 1. NO Manipulation of IV 2. NO Random assignment of subjects 3. NO Ability to draw cause and effect relations
  20. WHAT IS EXPERIMENTAL PSYCHOLOGY? Experimental psychology is the branch of psychology that deals with designing and carrying out experiments on behaviour & processes that underlie them. It is grounded in the experimental method where investigators systematically alter 1 or more variables, under controlled conditions, to determine whether such changes will influence another variable, Sensation, perception, learning, memory are some of the topics commonly studied
  21. Experimental group: Group that receives treatment or an active level of the IV Control group: Group not exposed to the treatment It receives a zero level of IV Purpose of the control group: To provide a standard of behavior to which the experimental group can be compared Experimental and Control Groups
  22. REPLICATION  Process of repeating a study to determine whether the Original findings can be duplicated  When the results are duplicated we can feel more confident about our conclusions  When they do not duplicate it may lead to better research & discoveries as scientist look for cues to explain why the results of one study what different from the other
  23. INTERNAL VALIDITY  Represents the degree to which an experiment supports clear causal conclusions.  If extraneous variables are controlled, we can be confident that the change in DV was caused by the change in IV (High internal validity)  However if we are unable to do so, it will have low internal validity as we cannot be show that the change in in DV was due to the manipulation of the IV
  24. EXTERNAL VALIDITY  This is concerned with whether the findings of an experiment are applicable to situations other than the one in which it was conducted  For example : Do findings obtained from a given sample generalize to the larger population from which the sample was selected ? Do findings of the study conducted in a lab generalized to everyday life ?