Each of the four interview, techniques allows substantially different levels of control over who is interviewed.
Personal interviews offer the most potential for control over the sample. An explicit list of individuals or households is not required.
Although such lists are desirable, various, forms of areas sampling can help the researcher to overcome most of the problems caused by the absence of a complete sampling frame.
In addition, the researcher can control who is interviewed within the sampling unit and how much assistance from other members of the unit is permitted.
Controlling who within the household is interviewed can be expensive. If the purpose of the research is to investigate household behavior, such as appliance ownership, any available adult will probably be satisfactory.
However, if the purpose is to investigate individual behavior, inter-viewing the most readily available adult within the household will adult, will often produce a biased sample.
Thus, the re-searcher must randomly select from among those living at each household. The simplest means of selection is to interview the adult who last had (or next will have) a birthday.
The odds of a-household member being at home are substantially larger than the odds of a specific household member being available.
This means that there will be more "not-at-homes:' which will increase interviewing costs substantially.
Personal and computer interviews conducted in central locations, such as shopping malls, lose much of the control possible, with home interviews because the interview is limited to the individuals who visit the shopping mall.
Mail questionnaires require an explicit sampling frame composed of addresses, if not names and addresses.
Such lists are generally unavailable for the general population.
Lists of specialized groups are more readily available However even with a good mailing list, the researcher maintains only limited control over who at the mailing address completes the questionnaire.
Different family members frequently provide divergent answers to the same question. Although researchers can address the questionnaire to a specific household member, they cannot be sure who completes the questionnaire.
Mailings to organizations have similar problems. It is difficult to determine an individual's sphere of responsibility from his or her job title.
In some firms the purchasing agent may set the criteria by which brands are chosen, whereas in other Fr-ms this is either a committee decision or is made by the person who actually uses the product in question.
Thus, a mailing addressed to a specific individual or job title may not reach the individual who is most relevant for the survey. In addition busy executives may often pass on a questionnaire to others, who are not as qualified to complete it.
Telephone surveys are obviously limited to households with direct access to telephone. However, the fact that telephones are almost universally owned does not mean that lists of telephone numbers, such as telephone directories, are equally complete.
As the current telephone directory becomes older, the percentage of households with unlisted numbers increases because of new families moving into the area and others moving within the area.
Each of the four interview, techniques allows substantially different levels of control over who is interviewed.
Personal interviews offer the most potential for control over the sample. An explicit list of individuals or households is not required.
Although such lists are desirable, various, forms of areas sampling can help the researcher to overcome most of the problems caused by the absence of a complete sampling frame.
In addition, the researcher can control who is interviewed within the sampling unit and how much assistance from other members of the unit is permitted.
Controlling who within the household is interviewed can be expensive. If the purpose of the research is to investigate household behavior, such as appliance ownership, any available adult will probably be satisfactory.
However, if the purpose is to investigate individual behavior, inter-viewing the most readily available adult within the household will adult, will often produce a biased sample.
Thus, the re-searcher must randomly select from among those living at each household. The simplest means of selection is to interview the adult who last had (or next will have) a birthday.
The odds of a-household member being at home are substantially larger than the odds of a specific household member being available.
This means that there will be more "not-at-homes:' which will increase interviewing costs substantially.
Personal and computer interviews conducted in central locations, such as shopping malls, lose much of the control possible, with home interviews because the interview is limited to the individuals who visit the shopping mall.
Mail questionnaires require an explicit sampling frame composed of addresses, if not names and addresses.
Such lists are generally unavailable for the general population.
Lists of specialized groups are more readily available However even with a good mailing list, the researcher maintains only limited control over who at the mailing address completes the questionnaire.
Different family members frequently provide divergent answers to the same question. Although researchers can address the questionnaire to a specific household member, they cannot be sure who completes the questionnaire.
Mailings to organizations have similar problems. It is difficult to determine an individual's sphere of responsibility from his or her job title.
In some firms the purchasing agent may set the criteria by which brands are chosen, whereas in other Fr-ms this is either a committee decision or is made by the person who actually uses the product in question.
Thus, a mailing addressed to a specific individual or job title may not reach the individual who is most relevant for the survey. In addition busy executives may often pass on a questionnaire to others, who are not as qualified to complete it.
Telephone surveys are obviously limited to households with direct access to telephone. However, the fact that telephones are almost universally owned does not mean that lists of telephone numbers, such as telephone directories, are equally complete.
As the current telephone directory becomes older, the percentage of households with unlisted numbers increases because of new families moving into the area and others moving within the area.
