Symmetric key block ciphers are the most widely used data encryption algorithm and is well known for its ability to protect against a wide range of attack. The effectiveness of a block cipher algorithm often depends on the size and strength of S-boxes. The Advanced Encryption Standard (AES) is presently the most widely used block cipher which stands as standard cryptosystem since more than two decades. Among the 30 irreducible polynomials over Galois Field GF(28), the S-box of original AES algorithm is designed using the first one. In this paper an initiative is taken to look statistically into the matter – if the irreducible polynomial is changed then what will be the effect on the security of the algorithm? It is observed that different irreducible polynomials over GF(28)can be used without compromising the strength of the original AES algorithm. This fact will help to generate a number of versions of AES algorithm that will increase its security.