RLD procedure

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The RLD procedure ( Engl. Randomized Last Digit : random last digit) is a method for determining sample at CATI surveys ( Computer Assisted Telephone Interview ) as part of market research or even of electoral research .

principle

A random phone number is generated by adding the last digit of any phone number to a random number between 1 and 9 or subtracting it from it. This means that households that are not recorded in the telephone book (subscribers with secret numbers ) can also be included in the (telephone) sample .

example

With the existing number 0511 - 555 1234 7 , the last digit - 7 - is replaced by a number that results from subtracting the random number 6 : 0511 - 555 1234 1 .

meaning

Because larger parts of the telephone connections are no longer registered in the official telephone book , this method of generating samples is becoming increasingly important, as there are large differences between the socio-demographic structure of registered and unregistered households.

The RLD process was developed in the USA and is now used by almost all leading market and opinion research institutes .