analysis and distributions Flashcards
what is a scatterplot?
display relations between two quantative variables
how to know if a relationship is strong or weak
- strong = points lie close to the line
- weak = points are widely scattered
what does it mean when variables are correlated?
variables are related
what is the purpose of a correlation analysis? (3)
determine
- if linear relationship
- direction of relationship
- strength of relationship
what are correlation coefficients
number between 1 and -1
tells us strength and direction of relationship
what does a positive correlation coefficent mean?
positive relationship
positive correlation
what does a negative corellation coeeficient mean?
negative relationship
negative correlation
what is the difference between linear and non linear relationship?
linear = measuring correlations okay
non linear = cant measure correlations
what are the two types of coefficient
- pearson r
- spearman r
what is pearson r coefficient?
- calculated from raw scores
- suitable for interval or ratio data
- highly affected by outliers
- not suitable for skewed data
what is spearman r coefficient?
- calculated from ranking raw scores
- suitable for ordinal data
- marginally affected by outliers
- suitable for skewed data
what is a density curve?
histogram distribution of scores of ppt
useful when lots of ppt
what do density curves show?
the overall pattern of a distribution
density curve + median
point that divides area into two equal parts
density curve + quartiles
point that divide area under curve into quarters