When you are approached by someone who claims to be a market researcher and then begins to ask a series of questions--some of them personal--how do you know if the interviewer is legitimate?

Rhoda Olchak, the president of Olchak Market Research Inc., Greenbelt, Md., and a representative of the Market Research Association, a trade group based in Chicago, Ill., says it's easy to spot a phony if you know what to look for.

As part of a public awareness and education campaign for National Marketing Research Week, which is being observed this week by the marketing research industry, Olchak said the Market Research Association developed the following tips to help consumers determine if the smiling person with the pencil, clipboard and questions is genuine or not:

* Beware of interviewers who aren't wearing or willing to show some form of identification. "All professionals are required by their employers to be able to identify themselves," Olchak said.

* Make sure you know the name, address and/or telephone number of the organization conducting the survey. Any hesitancy on the part of the interviewer to provide this information is immediate cause for ending the conversation.

* Decide if the questions sound appropriate. Remember that most surveys require both yes and no answers as well as responses that call for you to elaborate on your reasons for saying yes or no.

Criminals sometimes use the interview approach to gain access to personal information and private property enabling them to rob unsuspecting victims and their homes, Olchak said.

In addition, she said some marketing research companies have been guilty of "unethical conduct and outright gimmickry" in recent years, and as a result, some consumers refuse to volunteer information to professional market researchers.

The marketing industry now is trying to emphasize the importance of market research for companies and consumers, Olchak said.

One way to do that is to explain what the interviewers do and why, she said.

"What may sound like personal questions--such as age, income, education level and family makeup--are really legitimate questions that help the research user define the type of groups giving the answers," she said.