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25 Cards in this Set
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Measure of association

A general term that refers toa number of bivariate statistical techniques used to measure the strength of a relationship between two variables


correlation coefficient

a statistical measure of the covariation, or association, between two at least interval variables


covariance

extent to which two variables are associated systematically with each other


Negative (inverse) relationship

Covariation in which the association between variables is in the opposite direciton. As one goes up, the other goes down


Does covariation in and of itself establish causality?

No. Think of the example of the covariation between ice cream sales and drownings; or the roosters crow and the rising sun


Coefficient of Determination (R^2)

A measure obtained by squaring the correlation coefficient; the proporion of the total variance of a variable accounted for by another value of another value.
Measures that part of the variance of Y that is accounted for by knowing the value of X 

In the example about unemployment and hours worked, r = .635; therefore r^2=0.403
How much of the variance in unemployment can be explained by the variance in hours worked? 
About 40% of the variance in unemployment can be explained by the variance in hours worked.


Correlation Matrix

The standard form for reporting observed correlations among multiple variables. Although any number of variables can be displayed in a correlation matrix, each entry represents the bivariate relationship between a pair of variables.


What is the procedure for determining statistical significance?

The procedure for determining statistical significance is the ttest of the significance of a correlation coefficient


Simple (Bivariate) Linear Regression

A measure of linear association that investigates straight line relationships between a continuous dependent variable and an independent variable that is usually continuous, but can be a categorical dummy variable


In simple linear regression, what do the following symbols stand for:
Y (alpha) (beta) X (Y = (alpha) + (beta)X 
(alpha) represents the Y intercept, or where the line crosses the yaxis
(beta) is the slope coefficient The slope is the change in Y associated with a change of one unit in X. Slope may also be thought of as rise over run. 

True/False: Beta provides the strength and direction of the relationship between the independent and dependent variable

True


True/False: (alpha) Y intercept is a fixed point that is considered a constant

True


Standardized regression coefficient

Estimated coefficient of the strength of relationship between the independent and dependent variables
Expressed on a standardized scale where higher absolute values indicate stronger relationships (between 1 to 1) 

Raw Regression Estimates (b1)

Raw regression weights have theadvantage of retaining the scale metric (also their key disadvantage). Used if the purpose of the regression analysis is forecasting.


Standard Regression estimates ((Beta)1)

Have the advantage of a constant scale. Should be used when the research is testing explanatory hypothesis


Ordinary Least Squares

Generates a straight line that minimizes the sum of squared deviations of the actual values from this predicted regression line.


The equation for the ordinary least squares means that X estimated how?

The equation menas that the predicted value for any value of X is determined as a funciton of the estimated slope coefficient, plus the estimated intercept coefficient + some error


Where does the explanatory power of regression lie?

The explanatory power of regression lies in hypothesis testing


What two conditions must be satisfied for the outcome of the ypothesis test?

The regression weight must be in the hypothesized direction. (positivie relationships require a positive coefficient and negative relationships require a negative one)
The ttest associated with the regression weight must be significant 

Multiple Regression Analysis

An analysis of association in which the effects of two or more independent variables on a single, intervalscaled dependent variable are investigated simultaneously


Dummy Variable

The way a dichotomous (two group) independent variable is represnted in regression analysis by assigning 0 to one group and 1 to another


Partial correlation

The correlation between two variables after taking into account the fact that they are correlated with other variables too


R^2 in multiple Regression

The coefficient of multiple determination in multiple regression indicates the percentage of variation in Y explained by all independent variables


FTest

Tests statistical significance by comparing the variation explained by the regression equation to the residual error variation .
Allows for testing of the relative magnitudes of the sum of squares due to the regression and the error sum of squares 