There are different types of interviews and questionnaires, In this artiele, interviews will be investigated in terms of being structured or unstructured. AIso questionnaires will be investigated regarding its types which are 'selfadministered' and 'mailed' questionnaires, 1.1. Definitions of Interviews and Questionnaires Interview is a kind of conversation and as Hull (l) tells us ".. .but of Particularkind, where actors talk to a specific and conscious purpose." Channel and Kahn (1968) defined interview as "a two-person conversation initiated by the interviewer for the specific purpose of obtaining research-relevant information, and focused by him on content specified by research objectives of systematic description, prediction, or explanation" [cited in (2): p.271]. At its simplest form, a questionnaire is no more than a list of questions to which answers are being sought. However, to assure that misunderstandings or ambiguities in the questioning are reduced to aminimum, and to enable data to be compared across the members of a sample, a number of different ways of presenting questions have been developed (3). When constructing questions for interviews and questionnaires, Foddy (4) emphasizes that the researcher must elearly define the topic of each question, determine the applicability of the question to each respondent, and specify the perspective for responding to the question. 1.2. Types of Interviews When we look at the structured interviews, they can be the structured or unstructured. The structured interviews are that a list of questions is asked the answers recorded on a standardized schedule. The content and procedures are organized in advance for questioning. The sequence and wording of the questions are determined by means of a schedule and the interviewer is not allowed to make any changes. Fontana and Frey (5) emphasize that "There is generally little room for variation in response except where an infrequent open-ended question mav be used". Also thev add "There is very little flexibility in the way questions are asked or answered" . The unstructured interviews, contrary the structured interview is an open situation and so having greater flexibilityand freedom. Although research questions determine the questions to be asked, their content, sequence and wording are entirely left to the interviewer. However, this does not mean that the unstructured interview is a more casual thing, and for in its own way it must be carefully planned (2). 1.3. Types of Questionnaires There are two different types of questionnaires, namely the mail, and self administered questionnaires. As its name implies that mail questionnaires prepared questionnaire which are mail ed to the respondents whose names and addresses obtained regarding sample with co ver letter explaining the purpose of the survey emphasising how valuable the respondenfs completion of the questionnaire. A self addressed and stamped envelope for retums can also be included. The self-administered questionnaire is presented to the respondents by the researcher or by someone in an official position such as schools' headteachers. Holroyd and Harlen (9: p. 326) say that "Headteachers distributed the questionnaires to teachers of pupils. . ." The purpose of the questionnaire is explained, and then the respondents is left alone to complete the questionnaire, which may be sent or collected later. This method assures a high response rate, accurate sampling, and minimum of bias, providing necessary explanations and giying the benefit of personal contact (6). 2. THE COMPARISON OF INTERVIEWS AND QUESTIONNAIRES 2.1. Cost Interviews cost more money than questionnaires. Moser and Kalton (10: p.256) tell us."Without doubt, themail questionnaire is generally cheaper than other methods" and they continue by quoting from Selltiz et.al "Questionnaires can be sent through the mail; interviewers cannoL" There are traveling and existence expenses to be occurred, as well as payments to the interviews and interviewers. Interviewers have to be organized and trained which requires a field-work organization when interviewers are distributed all over the country . Granström (11: p.353) has found this factor as a difficulty in his research and he indicates that "About twice as many teacher applied, for which reason selection was based on practical factors, such as timetables and travelIina to expenses." As a result, he had to reduce the sample size. In some cases, interviewers leave or quit the survey. In this case the replacement of them presents some difficulties and cost some extra money. The interviewing of particular sample, such as following of the graduates of a school after five or ten years of graduation may be very expensive. The main advantage of the mailed questionnaire is its cheapness. Since it does not require a trained staff or the field workers, the payments to them and their travel expenses do not exisL Furthermore, all it requires the cost of planning and piloting, printing expenses, sampling, and mailing, providing stamped, self-addressed envelops for the retums. However, there is a danger of low response rate in mail questionnaire that it can make the survey expensive. "...the response to a mail survey may be so low that the cost per completed questionnaire is higher than with an interview sample." (10: p.257). Another advantage of the questionnaires is that their data processing and analysis is cheaper than that of interviews.