Consider a line of regression that fits data points showing

Consider a line of regression that fits data points showing crime rate and population for all U.S. cities with populations between 1 million and 10 million people.

a. For which U.S. cities would this line of regression not provide very good predictions of crime rate?

b. What advice would you provide to a sociologist from China who would like to use this line        of regression to predict the crime rate in Chinese cities?

c. What are some possible confounding variables that might covary with both crime rate and city population?

d. What would you say to someone who was convinced that high birth rates cause an increase in crime approximately 20 years later. Especially if he insists that this particular line of regression proves it (that is, assuming it has a positive slope)?

Solution

a) For US cities with population below 1 million and above 10 million this line of regression not provide very good predictions of crime rate.

b) Crime rates vary from place to place. Also China is an Eastern country with different culture and technology. Hence simply applying the regression line from US cities may

be irrelevent and misguidance..

c) Some confounding variables are the people\'s fear about committing crimes, (religious),

Punishment from law, Law and order situation, People Psychology, moral values, etc.

d) It may be true to some extent. High birth rates without corresponding death rates have an inclination to increase population with the available resources and area. This may lead to more demand than supply hence people with might and power may exploit to snatch from those who donot have. Thus this may increase the crime rate. But because simply positive slope, we cannot predict that the slope will be the exact value as it is for this regression line.

Fresh samples have to be taken for that period and slope arrived at.