Telephone Sampling Questions and Answers

from SRC Berkeley

About this Q and A
Some basic rules

Select a problem from the following list:

Answering Machines and Voice Mail

Answering machine all the time
Answering machine for a business
Answering machine refers to another number
Answering machine confirms different number
Answering machine then disconnected
Answering machine for a switchboard
Answering machines with no message
Answering machine for a fax
Voice mailbox services
Voice mail discontinued
Voice mail plus regular line

Cellular and Mobile Phones

Reached cellular phone
Cellular informant gave home phone

Fax and Computer Lines

Modem signals and busy
Apparent fax or modem signals
Computerized thank you

Multiple Phones in a Household

Teenager's phone
Refusal on teenager's phone
Telephone in a home office
Line used only for computer or fax
Business line forwarded to home
Phone number rings in two locations

Unusual Household Situations

House-sitter then disconnected
Residents away on sabbatical
House temporarily rented out
Caretaker for elderly person
Very big family
People about to move out
Phone number disconnected after enumeration
Phone number changed after enumeration
Construction worker at a house
Called a farm

Vacation Homes

Reached a cottage
Call forwarded to vacation location
Summer home for college student

Group Residences and Dorms

Switchboard of retirement home
Phone in a college dorm
Personal phone in college dorm

Bad phone numbers

Reach wrong number
Reach different but similar phone number
Phone always busy
Phone off hook
Temporarily disconnected or circuits busy
Funny signals
Beeps combined with no-answers
Circuit problems combined with busy signals

Interviewer errors

Interviewed wrong person
Miscoded outcome

About this Q and A

These questions arose during various telephone surveys conducted by SRC-Berkeley. The answers were provided by Tom Piazza, SRC Manager of Statistical Services. We welcome any discussion of the advice given here. Contact Tom at

Many of the questions concern the appropriate outcome or disposition code to assign to a case. Some outcomes mean that a case is excluded from the sample for purposes of calculating response rates -- unlike refusals or respondents who can never be found at home. See the discussion of basic rules for some general guidance on this matter.

Some Basic Rules

Most of the questions in this Sampling Q & A deal with the issue of whether or not a selected telephone number, in a random-digit sample, should be considered a valid residential number.

If the phone number is a residential one, it must be used in calculating the response rate, computed as the number of completed interviews divided by the total number of residential phone numbers in the sample.

If the phone number is NOT a residential one, it can be excluded from the denominator in the calculation of response rates. The issue is often to decide which outcome code or disposition to assign to a specific case.

Outcome codes that DO count against the response rate are the following:

Direct Refusal
Informant has refused to enumerate the household, or the selected respondent has refused to complete the interview.
Indirect Refusal
The interviewers were unable to get past a residential answering machine to talk to anyone, or a respondent has been selected but was never available to complete the interview,
Out of Town for Duration
The respondent (or everyone in the household, if this can be ascertained) is out of town for the duration of the study.
Unable to Participate
The respondent is eligible to be interviewed but is unable to participate because of some illness or disability.
Outcome categories that do NOT count against the response rate are the following:

Not in Service
Not a working phone number
Not a Residence
Business, computer line, etc.
Assumed not a Residence
This is a key category, since the status of many telephone numbers cannot be determined with certainty, and different organizations will devote different degrees of effort to making this determination. See below the rules followed at SRC-Berkeley.
No one in the household falls within the definition of the survey population. (For instance, the project may need to screen for certain age groups.)

Practical difficulties often arise because various calls to the same telephone number result in outcomes that are inconclusive or apparently inconsistent. For example, a phone number that usually rings (suggesting that it is a working number) can sometimes produce funny beeps (suggesting that it is Not-in-service). The problem is to develop rules to deal with these situations.

The procedures currently followed at SRC-Berkeley to resolve the status of a phone number with inconclusive calling outcomes -- that is, a phone number that no one has ever answered AND at which no answering machine with a message has ever been encountered -- can be summarized as follows:

(TP 2/23/96)