Chapter 1 Psychological Science Correlational Research

Correlation A statement of Relationship between two variables. One variable usually predicts the other.  Does ACT score predict future college success?  Does a high stress work environment predict chances of heart disease?  Does the education level of your parents predict whether or not you will drink?

Correlation Correlations can be positive or negative.  Positive correlation: As one variable increases or decreases, so does the other. Increased smoking, increased risk of lung cancer The less you study, the lower your grade  Negative correlation: As one variable moves, the other moves in the opposite direction. As exercise increases, chance of sickness decreases As self-esteem rises, depression levels decrease

Correlation  Correlation Coefficient  a statistical measure of the extent to which two factors vary together, and thus how well either factor predicts the other Correlation coefficient Indicates direction of relationship (positive or negative) Indicates strength of relationship (0.00 to 1.00) r = +.37

Correlation  Scatterplot  a graphed cluster of dots, each of which represents the values of two variables  the slope of the points suggests the direction of the relationship  the amount of scatter suggests the strength of the correlation  little scatter indicates high correlation  also called a scattergram or scatter diagram

Correlation Perfect positive correlation (+1.00) No relationship (0.00)Perfect negative correlation (-1.00) Scatterplots, showing patterns of correlations

Correlation Height and Temperament of 20 Men Subject Height in Inches Temperament Subject Height in Inches Temperament

Correlation Scatterplot of Height and Temperament Temperament scores Height in inches

Correlation and Causation It has been found that people with low self- esteem have a higher rate of depression than people with high self-esteem. Does low self-esteem cause depression?

Correlation and Causation Three Possible Cause-Effect Relationships (1) Low self-esteem Depression (2) Depression Low self-esteem Depression (3) Distressing events or biological predisposition could cause or and

Correlation and Causation Third Factor error  An unknown variable may be causing changes in both variables in question Directional error  The inability to determine which variable is the cause and which is the result

Illusory Correlation  Illusory Correlation  A belief that there is a relationship where none actually exists  A result of confirmation bias  Examples: Superstitions?

Two Hands Dealt in Poker

Two series of coin flips T-H-H-T-H-T-T-H-T-H T-T-T-T-T-T-T-T-T-T

Perceiving Order in Random Events  Your chances of being dealt either of these hands is precisely the same: 1 in 2,598,960. The chances of each series of coin flips is exactly the same because the chances of heads or tails on any one flip is 50%

Perceiving Order in Random Events The chances of a statistically improbable event happening to you is incredibly unlikely. That it should happen to someone at sometime is very likely. Consider This: An event happening to someone that has a 1 in a billion chance of happening, happens six times a day, every day.