correlation and regression Flashcards
what is the point of tests of relationship
see if there is an association between variables and if there is a cause and effect relationship
define correlation
change in 2 variables in the same direction at the same time
define regression
investigate the causal effect of one variable on another
what does regression assume
that one variable depends on the other (you can predict y from X)
relationship between X and Y for correlation
doesn’t matter which is y or x
regression or correlation?
you can predict y from x
regression
plot when you are looking at the relationship between 2 continuous variable
scatter plot
what does a scatter plot show you
the relationship between two continuous variables
you have two cntuniuous variables. what plot do you use to see their relationship
scatter plot
what’s it called when you are looking at whether two set of observations are associated
corrrelation
what’s it called when you are looking at how strong an association is
correlation
what does correlation tell you
whether observations are correlated and how strong or significant the association is
what t eat do you run to see if two observations are correlated
Pearson’s product-moment correlation, spearmint rank-order correlation or Kendall rank order correlation
what are the assumptions for Pearson’s correlation
- both variables are continuous
- both are normally distributed (bivariate normal distribution)
when would you use spearmans rank order correlation
if your variables are not normally distributed and you can’t run a Pearson’s correlation
NONPARAMETRIC EQUIVALENT TO PEARSONS PRODUCT MOMENT CORRELATION
spearmans rank order correlation
what tests if there is a linear relationship between variable
Pearson correlation coefficient
what do you use Pearson correlation coefficient for
to see if there is a linear relationship
explain what a value of r>0 indicates for Pearsons correlation coefficient
positive linear relationship
explain what a value of r<0 indicated for Pearsons correlation coefficient
negative linear relationship
explain what a v ally of r=0 indicates for Pearsons correlation coefficient
no linear relationship
what does linear correlation tell you
indicates whether variables are related (p<0.05), and how strong that relationship is
what influences p-values for Pearsons correlation
- sample size
- large N can give low P, even when effect (r) is weak
- high r can have non-significant p-values if N is low
how does r value impact results from Pearsons correlation
high r can have non-significant p-values if N is low