# Question: Researchers wondered whether the size of a person s brain was

Researchers wondered whether the size of a person’s brain was related to the individual’s mental capacity. They selected a sample of right-handed introductory psychology students who had SAT scores higher than 1350. The subjects took the Wechsler Adult Intelligence Scale-Revised to obtain their IQ scores. MRI scans were performed at the same facility for the subjects. The scans consisted of 18 horizontal MR images. The computer counted all pixels with a nonzero gray scale in each of the 18 images, and the total count served as an index for brain size.

(a) Draw a scatter diagram treating MRI count as the explanatory variable and IQ as the response variable. Comment on what you see.

(b) Compute the linear correlation coefﬁcient between MRI count and IQ. Are MRI count and IQ linearly related?

(c) A lurking variable in the analysis is gender. Draw a scatter diagram treating MRI count as the explanatory variable and IQ as the response variable, but use a different plotting symbol for each gender. For example, use a circle for males and a triangle for females. What do you notice?

(d) Compute the linear correlation coefﬁcient between MRI count and IQ for females. Compute the linear correlation coefﬁcient between MRI count and IQ for males. Are MRI count and IQ linearly related? What is the moral?

(a) Draw a scatter diagram treating MRI count as the explanatory variable and IQ as the response variable. Comment on what you see.

(b) Compute the linear correlation coefﬁcient between MRI count and IQ. Are MRI count and IQ linearly related?

(c) A lurking variable in the analysis is gender. Draw a scatter diagram treating MRI count as the explanatory variable and IQ as the response variable, but use a different plotting symbol for each gender. For example, use a circle for males and a triangle for females. What do you notice?

(d) Compute the linear correlation coefﬁcient between MRI count and IQ for females. Compute the linear correlation coefﬁcient between MRI count and IQ for males. Are MRI count and IQ linearly related? What is the moral?

## Answer to relevant Questions

The following data represent the number of licensed drivers in various age groups and the number of fatal accidents within the age group by gender. (a) On the same graph, draw a scatter diagram for both males and females. Be ...Lyme disease is an inﬂammatory disease that results in a skin rash and ﬂulike symptoms. It is transmitted through the bite of an infected deer tick. The following data represent the number of reported cases of Lyme ...Draw a scatter diagram that might represent the relation between the number of minutes spent exercising on an elliptical and calories burned. Draw a scatter diagram that might represent the relation between number of hours ...(a) By hand, draw a scatter diagram treating x as the explanatory variable and y as the response variable. (b) Select two points from the scatter diagram and ﬁnd the equation of the line containing the points selected. (c) ...The American black bear (Ursus americanus) is one of eight bear species in the world. It is the smallest North American bear and the most common bear species on the planet. In 1969, Dr. Michael R. Pelton of the University of ...Post your question