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26 Cards in this Set
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3 Difference scores issues (with mixed designs S/AxB)

1. masks main effects; only shows extent of change in A across B (interaction)
2. interpretation: oneway between groups ANOVA is computed but results must be interpreted as an interaction 3. if levels of B > 2, this fails 

what is Spearman Rho correlation? give example

correlation between ranks on two dimensions, ie hs class rank and college class rank


Pearson product moment:
ex: 
correlation between two continuous variables
self esteem and depression 

what does r estimate? between what and what?

r estimates rho. btw 1 and 1


what are the determinants of power for predicting y hat?

small N, small r


name the 3 cautions of hierarchical regression:

1. multicollinearity
2. suppression 3. shrinkage 

define mulitcollinearity, explain how it is fixed

high correlation among predictors, which explain the same variance and lower DF.
FIX: examine correlation matrix and eliminate a predictor, or combine predictors 

define suppression, explain fix

suppression is when the prediction of x1 is enhanced only because x2 suppresses variance irrelevant to y.
FIX: examine correlation matrix, if b's and r's have different signs, you have suppression! 

define shrinkage, explain fix

R squared is inflated as K increases (worse with small N).
FIX 2030 cases per predictor 

name the 3 assumptions of r

rectilinearity, homoschedasticity, x measured without error


define rectilinearity

relation is a STRAIGHT LINE


define homoschedasticity

variances of ys at each x are equal


what are the three caveats of r?

1. do not try to predict y beyond original range 2. do a scatter plot to look for leverage (outliers or extremes in mean) 3. truncated distributions reduce the size of r


what is the common language size effect?

if person A's x exceeds B's x, what is the probability that A's y will exceed B's y? CLE= y67, 67% chance


what does the multiple correlation and regression equation do?

comprizes more than one predictor, and minimizes squared differences of predicted y's from observed y's (least squares regression)


what is R?

correlation between obtained and predicted ys


R = ?

r times y times yhat
ALWAYS positive R is the best linear combination of the predictors of y 

explain a standard multiple regression

all variables added at once, each predictor is evaluated as though no overlap exists.


what is crucial about standard multiple regression?

each predictor is evaluated in terms of what it adds to the prediction of the criterion, that differs from predictability given by others


what test allows for assessment of unique contribution in standard multiple regression?

significance test of each regression coefficient (b)


what do these divisions of S/AxB design mean?: A, S/A, B, AxB, S/AxB

A = average variation between scores
S/A = error B = repeated measures factor AxB = interaction S/AxB = unexplained variability 

define these variables of S/AxB design: A, B, AB, a, an, b, bn

A = column totals
B = row totals AB = cell totals a = # levels of IV an = # of subjects b = # of times subject gives score bn = # of x's added to get A 

DF for S/AxB design:
total btw A S/A within B AxB S/AxB 
total: N 1
btw: an1 A: a1 S/A: btwA within: totalbtw B: b1 AxB: (a1)(b1) S/AxB: (S/A) times (B) 

what N is needed given projected effect for power?

4/rsquared = N1
this gives you 50% power double for 8090% power 

least squares regression:

Sigma (y  yhat)squared


in uncorrelated predictors, what does Rsquared tell us? R?

Rsquared: percent of variance in y explained by x
R: how strongly x1 x2 and y are correlated 