Research Methods Basic Methods Observational Experimental Observational Methods Observes behavior as it occurs in the real world One important observational method is correlation Correlation observes a relationship between two variables Correlation - Single Score Variable A Variable B Title goes here 1
Pairs of Scores I.Q. 150 100 50 0 0 1 2 3 4 GPA Positive Correlation Ranges from.01 to 1.00 example of weak correlation.20 example of strong correlation.90 As one variable increases so does the other Positive Correlation 140 130 I.Q 120 110 100 90 80 1 2 3 4 GPA Title goes here 2
Negative Correlation Ranges from -.01 to -1.00 example of weak correlation -.20 example of strong correlation -.90 As one variable increases, the other decreases Negative Correlation 6 5 Parties 4 3 2 1 0 1 2 3 4 GPA Example of Correlation Variable A - Watching Violent TV Measured by diary or log B Variable B - Aggressive Behavior Measured by observations in several settings A Title goes here 3
What does the correlation mean? Does it mean that watching violent TV causes greater aggression in children? A may cause B, but B may cause A Could more aggressive children watch more violent TV because they like it? Or C may cause both A and B Correlation, recap Measure relationship between two variables Don t know why they re related Why? Lack of control Title goes here 4
Experiment A scientist systematically manipulates one variable Called the independent variable And observes the effect of the manipulation On the dependent variable Examples of Independent Variables Drug treatment Method of teaching reading Exposure to television program Intellectual enrichment program for Down s syndrome children Dependent Variable In Psychology, dependent variables are always measures of behavior Examples Some cognitive score -- IQ, GPA, memory, problem solving Measures of adjustment or social skills Actual behaviors such as aggression or nurturance Title goes here 5
Experiment Select a sample from a population Assign at random to experimental or control group Random assignment allows you to know groups are equivalent at the start Hold everything constant except for independent variable (treatment) Experiment, cont d Measure dependent variable Do statistical test If groups differ significantly, there is only one possible reason the manipulation of the independent variable Can we say the independent variable caused the effect? Important Points about Experiments Random assignment allows you to know the groups are equivalent to start with The groups must be treated the same except for the independent variable The size of the groups is not as important as the representativeness of the sample Title goes here 6
Sample Experiment Looking at televised violence and aggression How would you do an experiment? What would the independent and dependent variables be? Sample Experiment Independent variable: exposure to televised violence Control group: exposed to some other televised content, not violence Measure aggressive behavior Compare experimental and control groups Sample experiment If the groups differ, can we conclude that exposure to the violence caused the difference? Yes, because no other difference between the groups Especially if the study is replicated However, the experiment may not generalize well to the real world Title goes here 7
Strengths and Weaknesses Of Observations Strength - Real world Weakness - No control or information about cause and effect Of Experiments Strength - information about causes Weakness - Artificial Conclusion You need both basic kinds of studies Many different studies of several types are needed to reach conclusions about any area Developmental Methods Cross sectional Studies Use different age groups e.g., 2, 4, and 6 year olds Longitudinal Studies Follow children as they age e.g., follow children from age 2 to age 6 Title goes here 8
Pros & Cons of Developmental Methods Cross Sectional Easy to do Different children, historical change Longitudinal Takes time to do Drop out Test-retest effects Same people, real developmental change Title goes here 9