15 Most (א A C D2 F G Ψ 0278 𝔐) have the plural τύπους (tupous, “examples”) here, while a few important witnesses have the singular τύπον (tupon, “example”; B D*,c 6 33 81 104 1739 1881 lat). With ὑμᾶς (humas, “you”) immediately preceding, the plural form looks motivated: Scribes would be expected to change the singular to the plural here. Although the external evidence for the singular reading is not overwhelming, the internal evidence for it is compelling.

In other versions

so that you became an example to all the believers in Macedonia and in Achaia.

And so you became a model to all the believers in Macedonia and Achaia.

As a result, you became an example to all the believers in Macedonia and Achaia.

As a result, you have become an example to all the believers in Greece—throughout both Macedonia and Achaia.

so that you became an example to all those who believe in Macedonia and in Achaia,

So that ye were ensamples to all that believe in Macedonia and Achaia.

Public Domain