Learn English – Artificial data or synthetic data

The difference is subtle, but in this case, Duplicate Data would be preferred. I would interpret the two phrases as follows:

Duplicate Data: Entries that have been added by a system user multiple times, for example, re-registering because you have forgotten your details.

Duplicated Data: Someone has deliberately taken a precise duplicate of the data - or a proportion of it - maybe for backup or reporting purposes. It may have been accidentally added to the original.

In the context of what you are talking about, the difference is important, because the second implies exact duplicates, whereas the first is a much more complex issue.

And yes, "exact duplicate" and "partial duplicate" are misnomers - it is either a duplicate or not - but these are the terms used.

AHD treats them as synonyms:

faux (foʊ)

adj. artificial or imitation; fake: faux pearls.

However, they are very rarely interchangeable, as Kris points out.

Faux has the connotation of 'accurate (more or less) representation / imitation with no moral intention to deceive'; it is a rather 'fancy' term (probably due to the obvious French derivation) useful to advertisers:

When manufacturing faux objects or materials, an attempt is often made to create products which will resemble the imitated items as closely as possible. However, some products are intentionally made to look "faux", for example, faux furs made for prospective buyers who want their fur to be recognizable as imitation due to controversy over the use and manufacture of real animal furs. [Wikipedia]

Artificial is the 'unmarked' term (artificial limb; artificial intelligence; artificial sweetner; artificial light) but can connote a lacking of a desirable quality ((of a person or a person's behavior) insincere or affected [Google]).

Fake has shady / tacky connotations (a fake Rembrandt; a fake gun).