A Researcher Examines the Correlations Between Identical and Fraternal Twins

Multiple Choice

A researcher examines the correlations between identical and fraternal twins' IQ scores in both higher- and lower-SES families. She prepares two line graphs of her results, one for higher-SES and one for lower-SES families. In both graphs, the y-axis is labeled "Correlation" and the x-axis is labeled "Degree of Genetic Resemblance" with increasing resemblance toward the right. What do the functions look like in the two graphs?

A) Higher-SES: positively sloped line
Lower-SES: horizontal line
B) Higher-SES: positively sloped line
Lower-SES: positively sloped line
C) Higher-SES: horizontal line
Lower-SES: positively sloped line
D) Higher-SES: horizontal line
Lower-SES: horizontal line