correlation studies

• correlation

  • used to measure the relationship between 2 variables
  • represented in a scattergram
  • positive correlation - as one variable increases so does the other
  • negative correlation - as one variable increases the other decreases
  • zero correlation - no relationship between the 2 variables
• coefficient 


  • a measure of the extent of the correlation that exists between the co variables
  • maximum volume of 1
  • coefficient must exceed 0.80
• linear 


  • all values line up almost in straight lines
• curvilinear 


  • the relationship is curved but there is still a predictable relationship (inverted U)
• strenghths

  • allow us to see if 2 variables are related
  • once we know there is a relationship, other types of study can be carried out to investigate this relationship
  • can be replicated
  • can be used when it would be unethical or impractical to manipulate variables
• limitations

  • correlations only show that there's a relationship
  • does not show cause and effect
  • involves measurement of 2 variables being investigated without control of extraneous variables
  • may lack internal/external validity
• hypothesis

  directional - "there will be a positive correlation between..."

  non directional - "there will be a correlation between..."