Unknown Eligibility

Unknown eligible is a category of survey dispositions that is used in all survey modes (telephone, in-person, mail, and Internet) when there is not enough information known about the case to determine whether the case is eligible or ineligible. For this reason, most survey organizations make additional contact attempts on cases categorized into one of the unknown eligibility categories to try to definitively categorize the case into either the eligible or ineligible category. Because the unknown eligible category is broad, researchers usually use a more detailed set of survey disposition codes to better categorize the outcomes of cases that fall into the unknown eligible category.

In a telephone survey, cases are categorized as unknown eligibles under two circumstances: (1) when it is not known whether an eligible household exists at a telephone number and (2) when it is known that a household exists at the number, but it is unknown whether an eligible respondent exists at the number. For cases in which it is not known whether a household exists at the sampled telephone number, cases of unknown eligibility include those numbers that were included in the sample but never dialed by an interviewer. Another common subcategory of cases of unknown eligibility include numbers that always ring busy, numbers that reach ambiguous answering machine or voicemail messages that do not indicate whether a household has been reached, privacy manager technologies that block interviewers from completing dialing attempts, and telephone line-related technical problems, such as “all circuits are busy.” If it is known that a household exists at the sampled telephone number, cases of unknown eligibility also can occur when it is not possible to complete a screener, and thus it is not known whether a household has an eligible respondent.

In an in-person survey, cases are categorized into the unknown eligibility category when one of two circumstances exists: (1) when it is not known whether an eligible household exists at an address and (2) when it is known that a household exists at the sampled address, but it is not known whether an eligible respondent lives at the address. For cases in which it is not known whether a household exists at the address, cases of unknown eligibility include those in which a household was not contacted by an interviewer (i.e. the case was not worked), cases in which an interviewer was unable to reach the household (most commonly due to causes related to safety and building security), and cases in which an interviewer was not able to locate the sampled address. If it is known that a household exists at the sampled address, cases of unknown eligibility also can occur when it is not possible to complete a screener, and thus it is not known whether a household has an eligible respondent.

Cases of unknown eligibility occur for five principal reasons in mail surveys of specifically named respondents. One reason that a case of unknown eligibility might occur in a mail survey is that the questionnaire was never mailed out, and thus, nothing is known about the sampled address. A second, more common, reason for a case in a mail survey being included in the unknown eligibility category occurs when the questionnaire was mailed out but the addressee did not receive the mailing. These cases include “refused by addressee,” cases in which the U.S. Postal Service will not deliver mail to the addressee, and cases in which the address on the outer envelope is incomplete or illegible. A third type of cases of unknown eligibility occurs in mail surveys when a case reaches a sampled address, but it is not known whether an eligible respondent resides at the address; this most often occurs when a screener is not [Page 931]completed. A fourth type of cases of unknown eligibility occurs in mail surveys when a questionnaire is returned as undeliverable but includes forwarding information. The fifth, and most common, case is those mailings for which the researcher never receives back any information on whether or not the mailing was received, including no returned questionnaire.

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