When a text is translated, depending on the audience for the translated text and depending on the importance of maintaining the correct information, there is a need for ensuring quality or for assessing the quality of translations. When there is a need for ensuring quality, it is in the choice of tools and procedures that quality can be expected.
There are many ways to improve the quality of translations. It is very much defined by the translation process. On the low end, machine translation will provide a fair idea of what the text is about while on the high end during the pre-translation, a glossary was created to ensure consistent the actual translation was done by a certified translator known for expertise in the domain using a CAT tool, the text is proofread by another certified translator or by a native domain expert.
Tools like online dictionaries and CAT tools even machine translations help translators. Making such tools part of a translation platform for volunteer translators does not only aid quality assurance, but the translators will likely be very grateful!.
Translation itself is often only a part of making information available. In Wikipedia for example, the original text is often not much more then the inspiration for the article in another language.When there is a need for a more exact translation, it is important to stress this need and a more formal setting helps.
When you have a text, translated or not, you can assess its quality. There are many levels of assessing a text; a domain expert assesses information, a linguist assesses the language used, anyone can assess if a text can be understood and someone bi-lingual can assess the translation.
To assess volunteer contributions it is important to appreciate the availability of the skills involved. It is harder to find people willing to translate in Tagalog or Ossetian then people for Spanish or Russian. When people identify themselves with a language, it helps when they can self organise themselves. When tools that support the translation process, people can choose to proof read and comment on the text and the translation as well as improve the text.
Readers of a text can be asked to comment on a text. A comment can be anything from a thumbs up/down, a five point vote to the commenting systems made popular by wikis.