Correlation and Experimentation Module 6

Correlational Research Detects relationships between variables. Attempts to predict behavior. Does NOT say that one variable causes another. There is a positive correlation between ice cream and murder rates. Does that mean that ice cream causes murder?

Measured using a correlation coefficient. A statistical measure of the extent to which two factors relate to one another. How well does one variable predict another?

(positive or negative) Correlation When one trait or behavior accompanies another, we say the two correlate. Indicates strength of relationship (0.00 to 1.00) Correlation coefficient r = + 0.37 OBJECTIVE 8| Describe positive and negative correlations and explain how correlational measures can aid the process of prediction. Correlation Coefficient is a statistical measure of the relationship between two variables. Indicates direction of relationship (positive or negative) Psychology 7e in Modules

Scatterplots Perfect positive correlation (+1.00) Scatterplot is a graph comprised of points that are generated by values of two variables. The slope of the points depicts the direction, while the amount of scatter depicts the strength of the relationship.

Scatterplots Perfect negative correlation (-1.00) No relationship (0.00) The Scatterplot on the left shows a negative correlation, while the one on the right shows no relationship between the two variables.

Data showing height and temperament in people.

Scatterplot The Scatterplot below shows the relationship between height and temperament in people. There is a moderate positive correlation of +0.63.

Practice with Correlations WKST – scatterplots and correlation coefficients

Correlation and Causation OBJECTIVE 9| Explain why correlational research fails to provide evidence of cause-effect relationships. Psychology 7e in Modules

Disconfirming evidence Illusory Correlation The perception of a relationship where no relationship actually exists. Ex: Parents conceive children after adoption. Confirming evidence Disconfirming evidence Do not adopt Adopt Do not conceive Conceive OBJECTIVE 10| Describe how people form illusory correlations. Michael Newman Jr./ Photo Edit Psychology 7e in Modules

Exploring Cause and Effect Experimentation Exploring Cause and Effect Like other sciences, experimentation is the backbone of psychology research. Experiments isolate causes and their effects. OBJECTIVE 12| Explain how experiments help researchers isolate cause and effect. Psychology 7e in Modules

Exploring Cause & Effect Many factors influence our behavior. Experiments (1) manipulate factors that interest us, while other factors are kept under (2) control. Effects generated by manipulated factors isolate cause and effect relationships.

Steps in Designing an Experiment Hypothesis Pick Population: Random Selection then Random Assignment. Operationalize the Variables Identify Independent and Dependent Variables. Look for Extraneous/Confounding Variables Type of Experiment: Blind, Double Blind etc.. Gather Data Analyze Results

Experimental Vocabulary Independent Variable: factor that is manipulated Dependent Variable: factor that is measured Extraneous/Confounding Variables: factors that effect DV, that are not IV. Experimental Group: Group exposed to IV Control Group: Group not exposed to IV Placebo: inert substance that is in place of IV in Control Group

Independent Variable An Independent Variable is a factor manipulated by the experimenter. The effect of the independent variable is the focus of the study. For example, when examining the effects of breast feeding upon intelligence, breast feeding is the independent variable. OBJECTIVE 14| Explain the difference between an independent variable and a dependent variable. Psychology 7e in Modules

Dependent Variable A Dependent Variable is a factor that may change in response to an independent variable. In psychology, it is usually a behavior or a mental process. For example, in our study on the effect of breast feeding upon intelligence, intelligence is the dependent variable.

Experiment Procedures Blind Procedure In evaluating drug therapies, patients should remain unaware of which group had the real treatment and which group had the placebo treatment. Double-blind Procedure In evaluating drug therapies, patients and experimenter’s assistants should remain unaware of which patients had the real treatment and which patients had the placebo treatment. OBJECTIVE 13| Explain why random assignment and double-blind procedure build confidence in research findings. Psychology 7e in Modules

The Placebo Effect https://www.youtube.com/watch?v=z03FQGlGgo0 https://www.youtube.com/watch?v=yfRVCaA5o18

Experiment Procedures Random Assignment Assigning participants to experimental (Breast-fed) and control (formula-fed) conditions by random assignment minimizes pre-existing differences between the two groups. Sometime research participants out of enthusiasm or personal beliefs can affect the out come of an experiment. To control for such affects, a double-blind procedure is used, in which the participants and the experimenter’s assistants are not aware of which participants got real treatment and who got placebo. Psychology 7e in Modules

A summary of steps during experimentation.

Below is a comparison of different research methods.

Common Pitfalls of Research Hawthorne Effect – you change your behavior b/c you are being watched Experimenter Bias Volunteer Bias Non-Random Sampling Confounding Variables Confusing Correlation for Causation Placebo Effect – experimental results caused by expectation of participant getting inert substance