What is your opinion about the methodology used to conduct this research?

Are police officers different from the rest of us?

Assigned Reading: Thistlethwaite & Wooldredge, Part 1 Chapter 1- Police Personality: Are police officers different from the rest of us? pp.4-11
After reading the article answer the following questions in a discussion posting:

What is your general opinion about the author’s research findings? 
This research was done in 1966, do you think its findings still apply today?
What is your opinion about the methodology used to conduct this research?
How would you improve on the author’s research?