In Rite I, there is an option to say the Nicene Creed with "I believe" instead of "We believe". This has a long standing tradition in Prayer Book history, all the way back to Thomas Cranmer. It actually has a history that is older than Cranmer himself.
There was a time in the church where priests began to say Mass privately. It seemed ridiculous to say "We believe" when the service got to the Creed with only one person present, so priests began to say "I believe" instead. It was not originally intended to reflect the individual and personal aspect of our faith, as one might think. It is instead the role of the Apostles' Creed to reflect our individual understanding and acceptance of the Christian Faith.
Eventually the practice of saying "I believe" in the Creed made it's way to public services, leading to it's usage all the way to modern times.
The "I believe" version of the Nicene Creed has a long history in the church and in our prayer book history both in the Episcopal Church and in the Anglican Communion. It also reflects the practice of private masses, a practice which Cranmer certainly would have disagreed with. Whether we would call this version of the Nicene Creed the traditional one depends on what you are referring to: Anglican Prayer Book Tradition or Early Church Tradition.
Tune in next week to learn more about the "We believe" version of the Nicene Creed!