Correlational Method Naturalistic observations, surveys, and case studies often show us that one trait or behavior is related to another. Correlation expresses a relationship between two variables. Does not show causation. As more ice cream is eaten, more people are murdered. Does ice cream cause murder, or murder cause people to eat ice cream?
Correlation Coefficient A statistical number that measures the strength of a relationship or how well one variable predicts another. Range is from -1 to +1 The relationship gets weaker the closer you get to zero. Which is a stronger correlation? -.13 or +.38 -.72 or +.59 -.91 or +.04
Scatterplots A graphed cluster of dots representing the values of two variables. The slope of the points suggests the direction of the relationship. Negative (Inverse) Correlation: Increases in one variable are matched by decreases in the other variable Positive (Direct) Correlation: Positive Increases in one variable are matched by increases in the other variable
Types of Correlation Positive Correlation The variables go in the SAME direction. Studying and grades hopefully has a positive correlation. Negative Correlation The variables go in opposite directions. Heroin use and grades probably has a negative correlation.
CAUTION!! Correlation Causation We can use correlation to describe a relationship and make predictions but it does NOT determine cause/effect Spurious Correlations
Illusory Correlation Perception of a relationship where none exists. Superstitions Old Wives Tales We deceive ourselves by seeing what is not there.
Experimental Method Looking to prove causal relationships. Cause = Effect Laboratory v. Field Experiments Smoking causes health issues.
First: The Participants (Subjects) The humans or animals participating in the research. Researchers look for differences between the dependent variable in the control and experimental groups to determine if the independent variable caused a change. Smoking causes health issues.
Random Assignment Once you have a random sample, randomly assigning them into two groups helps control for confounding variables. Experimental Group (receive the IV) vs. Control Group (not exposed to the IV).
Independent Variable Whatever is being manipulated in the experiment. Hopefully the independent variable brings about change. If there is a drug in an experiment, the drug is almost always the independent variable.
Dependent Variable Whatever is being measured in the experiment. It is dependent on the independent variable. The dependent variable would be the effect of the drug.
Beware of Confounding Variables If I wanted to prove that smoking causes heart issues, what are some confounding variables? The objective of an experiment is to prove that A causes B. A confounding variable is anything that could cause change in B, that is not A. Lifestyle and family history may also effect the heart.
IMPORTANT: IV and DV Follow these steps to make identification of the variables in an experiment easier to use.. 1. 2. 3. Convert the hypothesis into an if then statement. The IV is what comes after the if indicating the cause of the behavior studied The DV comes after the then indicating the expected effect of the IV.
IMPORTANT: Experimental and Control Groups Researchers exert control within an experiment by eliminating all differences between the two groups other than the IV. Methods include random samples, random assignment, and standardized procedures. The control group includes the participants within the experiment who do NOT receive the IV; they will be used for comparison with the experimental group to determine if there is a cause-effect relationship.
Hawthorne Effect But even the control group may experience changes. Just the fact that you know you are in an experiment can cause change. Whether the lights were brighter or dimmer, production went up in the Hawthorne electric plant.
Experimenter Bias Another confounding variable. Not a conscious act. Double-Blind Procedure - when neither the participant nor the research assistant collecting the data knows whether the participant s group is receiving the treatment.
Other Confounding Variables Placebo effect experimental effects caused by expectations alone; just believing you are getting a treatment can boost your spirits, relax your body, and relieve your symptoms. Well-documented in reducing pain, depression, and anxiety
APA Ethical Guidelines for Research IRB- Internal Review Board Both for humans and animals.
Animal Research Clear purpose Treated in a humane way Acquire animals legally Least amount of suffering possible.
Human Research No Coercion- must be voluntary Informed consent Anonymity No significant risk Must debrief