1.29.18
Topic 2: Methods
Correlation
●Correlational study- observes the relationship between variables
(moving in the same direction is still a positive correlation)
●Correlation coefficient: an estimate of
- direction of relationship
- strength (magnitude) of the relationship
●Info in the correlation coefficients
- strength: coefficients: -1 to +1, 0=no relationship
- direction: positive (+) or negative (-)
**which correlation coefficient is large? -.8 or .6 → (-.8)
1. Variable A could cause variable B
A-----> B
Ex. ice cream causing drowning
2. Variable B could cause variable A
A←---B
Ex. drowning causes increased in ice cream eating
3. Or a 3 variable could cause A and B
C→ A
→ B
Ex. Heat (when temp. Is higher outside we eat more ice cream and we go
swimming more often which may cause drowning.) ( A does not cause B)
Cross Sectional vs Longitudinal Designs
●Cross sectional design: data are collected at one point in time