Exam One - correlation and regression Flashcards
What is the goal of correlation?
evaluate the extent of a relationship between two continuous variables
What two things does the correlation coefficient tell us?
the strength and direction of the relationship
What letter is the correlation coefficient represented by?
lowercase r
______ = perfect inverse relation
-1
_______ = no relationship
zero
________ = perfect direct relationship
+1
coefficient of determination is represented by…
r^2
definition of coefficient of determination (r^2)
percentage of the total variance in Y scores that can be explained by X scores
______ r^2 values mean you can make more accurate estimates based on knowledge of one variable
higher
P value is inversely related to…
sample size and r value
magnitude of r relevance scale
0-0.25 = little to no relation
.25-.5 = fair relation
.5-.75 moderate/good
>.75 good/excellent
correlations (should/should not) be interpreted as being important if p-value is <0.05
should not
t or f? correlation determines causation
FALSE
coefficient r measures a linear or curvilinear relationship?
linear
values that are correlated are not…
necessarily similar
what is the goal of regression?
prediction
definition of regression
measurement variables used to develop an equation to predict one based on the other
in linear regression equation X is the ….
independent or predictor variable
in linear regression equation Y is the…
dependent variable or criterion variable
distance between the regression line and data point are called…
residuals
residuals are the…
extent of error for each observation relative to the repression line (prediction)
in equation Y = 64.72 + 1.39 (x) what is the dependent variable?
y
in equation Y = 64.72 + 1.39 (x) what is the independent variable?
x
in equation Y = 64.72 + 1.39 (x) what is the y-intercept?
64.72
in equation Y = 64.72 + 1.39 (x) what is the slope?
1.39
What units does r^2 use?
no units, just % of variability
_____ r^2 implies a more accurate prediction equation
higher
SEE
standard error of the estimate - magnitude of the expected error in Y based on the predictors
what units does SEE use?
the units of Y
_______ SEE implies a more accurate prediction equation
lower
95% CI of the prediction =
predicted value +/- (1.96*SEE)
multiple linear regression
method to predict the criterion variable based on more than one predictor variable
What two methods are possible for multiple linear regression?
- “enter” method
- forward, backward, or stepwise methods
enter method of multiple linear regression
this will use all variables in the prediction equation whether they make a meaningful contribution or not
forward, backward, or stepwise methods of linear regression
uses statistical criteria to max prediction accuracy using the fewest possible variables
_______- people per predictor variable are necessary when using multiple linear regression
7-15 (liberal)
The accuracy of multiple linear regression is evaluated by…
the coefficient of determination r^2 and the SEE
r^2
proportion of the variability in Y accounted for by all the predictors
SEE
expected error in our prediction of Y, expressed in units of Y
logistic regression
similar to linear regression, predicted variables are evaluated for the extent they accurately predict a CATEGORICAL outcomee
1 predictor: ____ logistic regresion
simple
> 1 predictor: _______ logistic regression
multiple
use of logistic regresion?
predicting categorical clinical outcomes
