week 8

• what are confounding variables

  • extraneous variables that change systematically along with the other variables being studied
  • threat to internal validity
• what must there be for an experiment to have internal validity

  1 and only 1 explanation for the research results
• what is assignment bias

  • the idea that all the people in one condition share one characteristic, and people in the other share another
• what are the types of correlation

  • positive
  • negative
  • zero
  • strong
  • weak
• in correlations, we look for covariance which ...

  tells us by how much two scores from two different variables differ from their respective means
• What is the covariance equation

  cov(x,y) = (sum(X-X BAR)(Y-Y BAR))/(N-1)
• What is the equation of variance

  var(x) = (sum(X-X BAR)(X-X BAR))/(N-1)
• How do we find the correlation coefficient (r)

  cov(x,y) / sd(x)sd(y)
• What is considered to be a small effect

  r is +/- 0.1
• What is a medium effect size

  r is +/- 0.3
• What is a large effect size

  r is +/- 0,5
• What is the coefficient of determination equal to

  r^2