correlations

• what does a correlation do

  measures the extent to which two variables are related.
• three possible results of a correlational study

  : a positive correlation, a negative correlation, and no correlation.
• positive correlation 


  a relationship in which both variables move in the same direction. Therefore, one variable increases as the other variable increases, or one variable decreases while the other decreases.
• what does a positive correlation graph look like


  starts at bottom and moves up
• A negative correlation 


  a relationship in which an increase in one variable is associated with a decrease in the other. 
• what does graph look like - negative correlation 


  starts at the top and goes down
• when does a zero correlation exist

  when there is no relationship between two variables. For example, there is no relationship between the amount of tea drunk and the level of intelligence.
• which graph is appropriate to use and why

  scattergram (plot as crosses and draw line) , it indicates the strength and direction of the correlation
• uses of correlations 


  1. predictions about how the variables are related
  2. validity (concurrent) correlation between new test and existing test
  3. testing reliability
• what is a correlation coefficient

  instead of using a scattergram it can be expresed numerically as a coefficient ranging from -1 to +1

  • 1 being a perfect positive and -1 a perfect negative
• why is correlation not causation

  it only shows a relationship between the variables, does not manipulate variables