Final session 11a Flashcards
what are Two of the most versatile approaches for investigating variable relationships
Correlation analysis Regression analysis
Both regression-based methods and ANOVA are subsumed by what
the general linear model
Regression-based methods subsume ANOVA, ANCOVA, etc.
This means that what
ANOVA models can be done in a regression analysis framework
The language and notation used to describe ANOVA is just different
what are ANOVA-based methods
Categorical independent variables (IVs):
Only interactions among categorical IVs are allowed
Continuous “covariates” can be added as IVs (ANCOVA)
explain Regression-based methods
Categorical and/or continuous IVs
Interactions among both types of IVs are possible
how many DV are in regression-based and ANOVA-based methods
just 1
A scatterplot shows what
the relationship between two quantitative variables measured on the same individuals
scatterplots It helps us understand the . . .
Form (linear or nonlinear?) Direction (positive or negative?)
Strength (none, weak, strong?)
of the relationship
A scatterplot is a graphical display of the relationship between what
two quantitative variables
The relationship examined by our eyes may not be satisfactory in many cases
what often supplement the scatterplot graph
Numerical measures often supplement the graph Example: Correlation
The Pearson correlation measures what
the direction and strength of the linear relationship between two quantitative variables
Pearson correlation coefficient (r)
The Pearson correlation coefficient is a what
standardized covariance
Covariance indicates what
how much X and Y vary together
Interpreting Covaraince:
Cov(X, Y ) > 0:
X and Y tend to move in the same direction
If X and Y tend to increase (or decrease) together → positive
Interpreting Covaraince:
Cov(X, Y ) < 0:
X and Y tend to move in opposite directions
If X increases when Y decreases → negative
Interpreting Covaraince:
Cov(X, Y ) = 0
X and Y are independent
Otherwise, the size of the covariance is difficult to interpret
It depends on the scales (or units, or variances) of X and Y
Pearson correlation coefficient (r) Compute from what
covariances and variances
is the Correlation coefficient sensitive to the units of X and Y
Not sensitive to the units of X and Y
Rescaling X and Y does not change the correlation between them
The Pearson correlation coefficient can be understood as the what
Covariance between z-scores for X and Y :
for correlation, explain The closer to −1,
the stronger the negative linear relationship
for correlation, explain The closer to 1,
the stronger the positive linear relationship
for correlation, explain The closer to 0,
the weaker any linear relationship
does correlation indicate causation
Correlation does NOT indicate any causal relationship among variables
True of false: A strong correlation between two variables does not mean that changes
in one variable cause changes in the other
true