Correlation and Regression Flashcards
When two variables are measured on a continuous scale and the relationship between the variables is nonlinear, you would use which of the following to determine the degree of association between the variables?
A. eta coefficient
B. contingency coefficient
C. biserial coefficient
D. Pearson r
Answer A is correct. Eta is the alternative to the Pearson r for calculating the correlation between two continuous variables when the variables have a nonlinear relationship.
For a sample of middle school students with high IQs, the correlation between IQ scores and achievement test scores is .35. If the correlation between IQ scores and achievement test scores is calculated for a sample of middle school students whose IQs represent the full range of IQ scores, the correlation coefficient is likely to be:
A. .35
B. larger than .35.
C. smaller than .35.
D. smaller or larger than .35
Answer B is correct. The scores used to obtain the original correlation coefficient had a restriction in range because the sample included only students with high IQs. A restricted range of scores tends to lower the correlation coefficient, so recalculating the coefficient for students with an unrestricted range is likely to produce a larger correlation coefficient.
To determine the relationship between cigarette smoking and absence from work, Dr. Nunez obtains a sample of employees who are either smokers or nonsmokers and determines the number of days each employee was absent from work the previous year. Dr. Nunez will use which of the following to calculate the correlation between these two variables?
A. Pearson r
B. Spearman rho
C. point biserial coefficient
D. contingency coefficient
Answer C is correct. The point biserial coefficient is used when one variable is a true dichotomy (smokers versus nonsmokers) and the other is continuous (number of days absent from work). (A useful mnemonic for distinguishing between the point biserial and biserial coefficients is to use the “t” in point as a reminder that the point biserial coefficient is used when one variable is a true dichotomy.)
You would use stepwise multiple regression when you want to:
A. identify the fewest number of predictors needed to make accurate predictions about scores on a criterion.
B. identify the fewest number of predictors needed to accurately categorize people into two or more mutually exclusive criterion groups.
C. identify the predictors that have a causal relationship with the criterion.
D. identify the optimal number of criterion groups.
Answer A is correct. Stepwise multiple regression involves adding or subtracting one predictor at a time to the multiple regression equation in order to identify the fewest number of predictors that are needed to make accurate predictions about scores on the criterion.
Which of the following is the appropriate technique for using measures of severity of depression, anxiety, drug/alcohol use, and cognitive impairment to classify individuals with major depressive disorder as being at risk or not at risk for suicide?
A. regression analysis
B. multiple regression
C. canonical correlation
D. discriminant function analysis
Answer D is correct. Discriminant function analysis is the appropriate multivariate technique when two or more predictors will be used to estimate status on one nominal (grouping) variable.
Which of the following best describes the variables included in a structural equation model?
A. Manifest variables cannot be observed directly, and their influence is inferred from indicator variables.
B. Latent variables cannot be observed directly, and their influence is inferred from indicator variables.
C. Manifest and latent variables cannot be observed directly, and their influence is inferred from indicator variables.
D. Manifest variables cannot be observed directly, and their influence is inferred from latent variables.
Answer B is correct. In structural equation modeling, observed variables are also known as manifest variables and indicators and are directly observed and measured. Latent variables are also known as factors and constructs and cannot be directly observed or measured but are inferred from observed variables.
A psychologist finds that the relationship between physiological arousal and motor performance for a sample of athletes is .40. This means that ___% of variability in motor performance is explained by variability in physiological arousal.
A. 60
B. 40
C. 36
D. 16
Answer D is correct. A correlation coefficient between two different variables can be squared to calculate the coefficient of determination, which indicates the amount of variability in one variable that’s explained by variability in the other variable. The psychologist obtained a correlation of .40 between arousal and motor performance, and .40 squared is .16. This means that 16% of variability in motor performance is explained by variability in arousal.
