Chan-ju and Lucas are researchers studying consumer behavior. Chan-ju goes to a store and watches ...

Chan-ju and Lucas are researchers studying consumer behavior. Chan-ju goes to a store and watches the shoppers for several days. She takes very careful notes about what she sees the shoppers doing, but she does not talk to the shoppers or interact with them in any way. Lucas goes to a store and asks each shopper a series of questions. He makes sure to ask these questions of each shopper in the store. Chan-ju's study is an example of a(n) ____, and Lucas's study is an example of a ____.
 
  a. case study; naturalistic observation
  b. experiment; case study
  c. survey; survey
  d. naturalistic observation; survey