Correlation and Regression

1. Correlation and Regression

2. Today�s Objectives Develop the term Construct Validity Introduce the use of correlation as a means of validating a test instrument Express the extent to which two measures are associated using r

3. Self Esteem "Our lives are shaped by those who love us and by those who refuse to love us." - John Powell S.J. How has self esteem been operationalized? National Association for Self Esteem Self Esteem Test

4. Self Esteem Governor Deukmejian set up a task force in the 1980�s on self-esteem and personal and social responsibility. The results: "many, if not most, of the major problems plaguing society have roots in the low self-esteem of many of the people who make up society.�

5. Self Esteem Happiness and Self Esteem Among 13,000 college students, high self-esteem emerged as the strongest correlate of overall life satisfaction (Diener). Data from more than 600 adults ranging in age from 51 to 95 showed happiness and self-esteem were closely tied (Lyubomirsky, Tkach, & DiMatteo, 2004).

6. Self Esteem Self-esteem and Academics Self-esteem in 10th grade is only weakly predictive of academic achievement in 12th grade (Pottebaum, Keith, & Ehly, 1986) Self-esteem and Risky Behavior Teenagers with high self-esteem are less inhibited, more willing to disregard risks, and more prone to engage in sex. Self-esteem measured between ages nine and 13 did not predict drinking or drug use at age 15 (McGee & Williams, 2000) Bad sexual experiences and unwanted pregnancies appear to lower self-esteem. Artificially boosting self-esteem may lower subsequent performance. Studies of possible links between workers' self-regard and job performance echo what has been found with schoolwork. Artificially boosting self-esteem may lower subsequent performance. Studies of possible links between workers' self-regard and job performance echo what has been found with schoolwork.

7. Self Esteem Duane P. Buhrmester and colleagues found that self-regard was positively associated with interpersonal skill, including: Ability to Initiate relationships Self-disclosure Assertiveness Providing emotional support Ability to manage interpersonal conflicts.

8. Self Esteem However, when participant�s self regard scores were correlated with their roommates' ratings of their interpersonal skills, only the subjects' ability to initiate new social contacts and friendships was statistically significant.

9. Self Esteem Let�s take a step back. �people who have healthy or authentic self-esteem � trust their own being to be life affirming, constructive, responsible and trustworthy� Are we measuring self-esteem? Or how socially desirable people think they are? Or ???

10. Construct Validity Refers to the degree to which inferences can legitimately be made from the way in which a construct was operationalized in a study to the theoretical constructs on which those operationalizations were based. When a researcher claims that their construct has validity, they are essentially claiming that the observed pattern among measures-- how things relate together empirically, or in reality -- corresponds with the theoretical pattern that they proposed.

11. Construct validity and correlation �Job stress�

12. Construct Validity Unskilled Laborer Secretary Assembly-line inspector Clinical Lab Technician Foreperson Manager/Administrator Clothing sewer Garment checker Stock clerk Skilled craftsperson Housekeeper Farm Laborer

13. Introducing Covariance

14. Introducing Covariance

15. Introducing Covariance

16. Introducing the Covariance By dividing the covariance by sxsy, we�ve standardized it. The value of the index will range between 1 and -1. The larger the absolute value of this index, the stronger the association between two variables.

17. Introducing the Covariance When expressed this way, the covariance is called a correlation The correlation is defined as a standardized covariance.

18. And it just keeps getting better� It can also be defined as the average product of z-scores because the two equations are identical.

19. Correlation

21. Calculating r

23. Linear Regression

24. Credits Sir Francis Galton Invented the statistical concepts of correlation and regression First to apply statistics to study human individual differences and inherited differences in intelligence He was Darwin�s half cousin

25. Credits (and a cliff hanger) Sir Francis Galton Noted that tall men tended to have sons who were a little shorter than they, and unusually small men tend to have sons that were closer to the average height. Galton thought of this as regression toward mediocrity. Can you think of any alternative explanations (Galton eventually did!)?