With each of the following examples, compose a reasonable statement of an association you would expect to find existing between the factors involved, and construct a stacked bar chart expressing that association.

a. Wearing of braces to straighten teeth by children attending expensive private schools versus those attending public schools

b. Having a Doberman pinscher as a guard dog, use of a home security alarm system, and ownership of rare pieces of art

c. Adherence to the "diet pyramid" recommended by the Surgeon General of the United States for healthful living and family history of heart disease

d. Purchases of toys as gifts during the Christmas buying season versus other seasons of the year by parents of preschool-aged children.