Where the Old Testament is concerned, the King James Version  (KJV), the New International Version (NIV), as well as most Protestant translations of the Bible are based on a single manuscript, the Leningrad Codex, produced around 1008. This Codex is our earliest complete copy of the Masoretic Text of the Hebrew Bible.  The text was primarily edited, fixed and standardized from old Hebrew manuscripts by a group of Jewish scholars known as the Masoretes in Tiberias, Israel, between the 7th and 10th centuries C.E.  The aim of these scholars was to follow in and maintain the traditions of the first Masoretes scholars in keeping a faithful watch over the preservation of the biblical texts, which were revised, set in order and interpreted by the Sopherim, Levite scribes, after the return of the Jews from Babylon to Palestine under the leadership of Ezra and Nehemiah.

Another translation of the Hebrew Bible, begun in the third century B.C.E., the Septuagint, was produced by Hellenistic Jews living in Alexandria, Egypt.  This translation was in Greek, since it was the language adopted by Jewish scholars, who, now living abroad, had lost fluency in Hebrew.  The Septuagint, however, differed from the Masoretic Text in that it comprised fourteen additional books known as the Apocrypha.  The famous KJV of 1611, though based on the Masoretic Text, did contain the Apocrypha.  Historians differ as to whether King James demanded its inclusion or fought against it.  The fact remains that Martin Luther, although he did not regard the Apocrypha as part of the Holy Scriptures, included it in his 1534 German translation of the Bible, though he placed it between the Old and the New Testaments, deeming these books to be “good to read”!  In the early nineteenth century, the Puritans and the Presbyterians pressured the British and Foreign Bible Society (BFBS) to do omit the Apocrypha, and by 1826 these books were removed from the KJV.  The NIV, produced in full in 1978, is also primarily based on the Masoretic Hebrew Text, though other texts, such as the Dead Sea Scrolls, the Latin Vulgate, etc. were likewise consulted.  It does not include the Apocrypha.

For the New Testament, the KJV uses the Textus Receptus or Received Text.  It is the Greek New Testament text from which the writings of the apostles in Koine (common) Greek were later translated.  During the Dark Ages, this Textus Receptus was unknown outside the Greek Church. Erasmus restored it to Christendom, though. Lucian of Antioch’s contribution in verifying, safeguarding and transmitting the sacred writings is paramount. The Textus Receptus was based on only ten Greek manuscripts (none older than the 10th century).  It is not flawless, and does contain added spurious passages, such as the one in I John 5:7: the phrase “and these three are one” does not appear in older Greek manuscripts. Textus Receptus is by far inferior to the Nestle-Aland New Greek Testament. Interestingly, it was not favored by the Roman Catholic Church, which endorsed the Latin Vulgate. 

The Greek text used in translating the NIV’s New Testament is not   the Textus Receptus but an “eclectic text”.  This version of the Bible maintains that the best available and current printed texts were utilized.  It is an eclectic text because where the Greek manuscripts differed, the choice of variants was based on the majority vote of a committee of more than 100 scholars, according to accepted principles of New Testament textual criticism.  A thought-to-thought translation was preferred to an exact word-to-word rendition of the text, thus facilitating interpretation.  For these reasons the theological bias of the NIV remains suspect.