Back Translation is the process of translating a document that has already been translated into a foreign language back to the original language - preferably by an independent translator
Translation of raw data such as focus group transcripts back into the language of a client from the language of the consumers is common in market research in Asia. In fact translation remains one of the costliest parts of a market research project. This is because it is an area where costly errors can be built in - in research stages where checks and balances are limited.
The nuances of translation are far-ranging. A literal word in one language, for example, may have no equivalent in another language, or could have a completely different "meaning" or effect in the translated language. This is why translation is an art rather than a science. No translation can be expected to convey perfectly the "meaning" of what consumers meant to convey in their own language. Hence the need for accredited translators who can translate verbatim. All the good work of a focus group moderator in not "interpreting" verbatim comments can be wiped out by a careless translator.
Back translation can improve the reliability and validity of research in different languages by requiring that the quality of a translation is verified by an independent translator translating back into the original language. Original and back translated documents can then be compared.
Due to its high cost, back translation is not overly common, but in very high risk - high return situations is well worth the investment.