Final answer:
The most variable position within a codon that still allows the same amino acid to be encoded is the third or 'wobble' position due to the degeneracy of the genetic code.
Step-by-step explanation:
The most variable triplet position in terms of coding for the same amino acid is the third position within a codon. This position is often referred to as the wobble position. The redundancy in the genetic code is known as degeneracy, where the third position can vary without necessarily changing the amino acid that is incorporated into a growing polypeptide.
While the first two positions in a codon are critical for determining which amino acid is incorporated, the third position is less critical, and variations here can still result in the same amino acid being incorporated due to the nature of the genetic code. Thus, a mutation in the third base often still permits the correct amino acid to be included in a protein sequence.