Correlation and Experiments (Cont. of Psychology is a science.) Chapter 1 – Myers Chapter 2 – Barron’s

Review – Last class Descriptive Methods Case Study Survey Naturalistic Observation

Correlation Correlation – measures the relationship between two variables Correlation coefficient: a statistical measure of the extent to which two factors vary together, and thus of how well either factor predicts the other. A correlation means that there is an association between two factors.

Examples of Correlations Ex. of some correlations Thin people live longer Overweight people earn less money than their peers School uniforms decrease school violence Handedness (L or R) and driving skills Juvenille Delinquincy and growing up in a single parent home The Marshmallow Experiment & Time Oh, The Temptation

Correlation The correlation coefficient shows two aspects of a relationship Direction (Positive or negative) Strength (how close to 1.00 OR -1.00) Correlation coefficients range between and Number shows Strength + or – shows Direction Positive – direct relationship Negative – inverse relationship Exercise on this AND Live!PsychLive!Psych

Correlation Coefficient Correlation Coefficients Explanation Perfect positive correlation – an increase in one factor will always be matched by an equal increase in the other factor Positive correlation – as one factor increases the second factor tends to increase. (Can range from to +0.01) 0.00Zero correlation – no relationship between the two factors. This is the weakest possible correlation Negative correlation – as one factor tends to increase, the second factor tends to decrease Perfect negative correlation – an increase in one factor will always be matched by an equal decrease in the other factor.

Correlation and Causation Correlation does NOT prove causation Correlation indicates the possibility of a cause and effect relationship Correlation may be due to coincidence Ex. Ice Cream consumption and rapes. Correlation may be due to other factors (confounding variables). Q Correlation between juvenille delinquincy and growing up in a single parent home?

Illusory Correlations Illusory Correlations: the perception of a relationship where none exists When I wash my car, it always rains As the number of ice cream sales increases, the number of murders increases Those who adopt a child are more likely to conceive.

Experiments Experiment – a research method is one which an investigator manipulates one or more factors (IV) to observe/measure the effect of some behavior or mental process (DV). Only experiments can identify cause and effect relationships

Experimental Conditions Experimental condition – to expose a participant to treatment (Ex. pill increase focus when taking tests). Control condition – contrast to the experimental condition. Serves as a comparison in that this subject does not receive treatment OR receives a placebo. Confounding variable – any difference between the experimental and control conditions, except for the independent variable. One can control for confounding variables by random assignment. Exercise: Ruler Experiment

Random Assignment Random Assignment (ONLY Used in the experimental method) is the process by which subjects are placed into an experimental or control group. Random assignment limits the effect of subject- relevant confounding variables. (outside factors of the subject other than the IV).

Controlling for all other variables Equivalent environments control for situation-relevant confounding variables. Room temperature, test administrator with a cold Random assignment controls for subject- relevant confounding variables. What if each student got to pick the group in which he/she wanted to take part? Experimenter bias (when the experiment wants or expects certain results) can be eliminated by using double blind procedure.

Variables Independent Variable – the experimental factor that is manipulated. This is the variable being studied. Dependent variable – the experimental factor that is being measured. This is the behavior or the mental process. This variable may change depending on manipulations in the IV. Live Psych slides 3 (IV and DV) and 5.(Op def.)

IV and DV If one receives more sleep before a test he/she performs better IV – Sleep DV – Test Scores Does the use of color of a football jersey affect perception of referees. IV – watching football plays with a team wearing black DV – amount of penalties called. Activity: Hunting for Causes

Example Experiment Hypothesis – This pill will lower hyperactivity in children with ADHD Independent Variable – receiving the pill Dependent Variable – level of hyperactivity Experiment Design - Students with ADHD are randomly assigned to a group. Exp. Group receives pill while the control group receives a placebo (fake pill). A month later students level of hyperactivity is measured

Double Blind Blind – unaware of what treatment is received Double Blind - participants and research staff are ignorant about the treatment/placebo given to each subject. Double blind procedures can eliminate subject and experimenter bias. Why could this be beneficial in a study? Research expectations can also affect how a patient acts/reacts to certain treatment Essential in drug research to control for self-fulfilling prophecies, placebo effects, or biases from the experimenters.

Methods of Eliminating Bias Random Sample Random Assignment Placebo (if a experiment is drug related) Double Blind Replication

Placebo Effect Placebo Effect - results caused by expectations alone. Using a Placebo - One group receives the treatment (drug being tested) the other receives a pseudo treatment (placebo). Ex. In the Korean War patients were given placebos when they ran out of morphine. Most patients reported a reduction in pain. Ex. College freshman were given 6 non-alcoholic beers to drink in 2 hours. Most exhibited some intoxicating behaviors. Penn and Teller: Placebo Effect

Hawthorne Effect Research in which workers were monitored to see if the amount of light in a room would affect worker productivity. Under both conditions, performance increased because subjects were being watched. The Hawthorne Effect states that people tend to act atypical having been chosen for an experiment. The Hawthorne Effect complicates experiment design

Experiments aim to …. MANIPULATE the IV MEASURE the DV CONTROL for all other factors through random sampling Prove a CAUSE AND EFFECT relationship

Correlation vs. Experiment In pairs (or by yourself), state whether research is correlational or experimental. If it’s correlational state whether it’s positive or negative. If it’s experimental state the IV and the DV.