CorrelationsAP Psychology

Correlations

Co-relation It describes the relationship b/w two variables.

Example #1 How is studying related to grades? # of hours a student studies for an exam scores on the examsFind: as their hours of study increased, their grades

increased.

Positive correlations

• Indicates a direct relationship between variables.

• An increased in one variable is accompanied by an increase in another variable or a decrease in one variable is accompanied by a decrease in another variable.

Example #2

• How is television viewing related to grades? ask an individual to calculate the average

# of hours a day he or she watches. Grades could be measured by the grade

point average obtained at the end of the school year.

May find: amount of TV. increased, GPA decreased.

Negative Correlation

• Indicates an inverse relationship b/w variables; an increase in one variable is accompanied by a decrease in another variable.

Think of correlations this way

• correlation is a lot like a relationship between a couple:

• If you have a positive relationship you both are headed in the same direction.

• If you have a negative relationship you go your separate ways.

How are correlations measured?

Correlation Coefficients.• Correlations are measured with #’s ranging from

-1.0 to +1.0• +1.0 and -1.0 are Perfect Correlations• 0 indicates no correlation b/w variables.As the # increases toward +1.0, the coefficient

shows an increasing positive correlation.As the # moves closer to -1.0, the stronger the

neg. correlation b/w variables.

Continue from previous slide

• Examples:• +.79 and -.79 are both strong correlations• -.22 is a weak correlation• Remember that the (+) and (-) indicate the

direction of the relationship.

Causation?

• CORRELATION DOES NOT IMPLY CAUSATION.• Correlation research is a process that indicates

the probability that when one variable exists, the other variable will also be present or affected.

Scatter Plots/Grams

• Can give a visual representation of correlations.

More Scatter Plots examples

Scatter plots

Scatter plot examples

Scatter plot example

What is an IV and a DV in a correlational study.

• Though a researcher is not directly manipulating a situation (such as in an experiment), he/she is manipulating the data (choosing what to look at).

• I am doing a correlational study trying to find a correlation between height and income.

• My IV is height (since I have chosen or grouped people by height, it is what I chose to manipulate), my DV is income.

• I do a correlational study looking for a relationship between grade level and test scores.

• My IV is grade level, my DV is test score.