an alternative expression for the constant c4[n] with desirable properties

The constant c4[n] is commonly used in the construction of control charts and the estimation of process capability indices, where n denotes the sample size. assuming the normal distribution the unbiased estimator of the population standard deviation is obtained by dividing the sample standard deviation by the constant c4[n]. an alternative expression for c4[n] is proposed, and the mathematical induction technique is used to prove its validity. some desirable properties are described. first, the suggested expression provides the exact value of c4[n]. second, it is not a recursive formula in the sense it does not depend on the previous sample size. finally, the value of c4[n] can be directly computed for large sample sizes. such properties suggest that the proposed expression may be a convenient solution in computer programming, and it has direct applications in statistical quality control.