# Question: a Discuss the use of the moving range method to

(a) Discuss the use of the moving range method to estimate the process standard deviation when the data are positively autocorrleated.

(b) Discuss the use of the sample variance s2 with positively autocorrelated data. Specifically, if the observations at lag i have autocorrelation i, is s2 still an unbiased estimator for 2?

(c) Does your answer in part (b) imply that s2 would really be a good way (in practice) to estimate 2 in constructing a control chart for autocorrelated data?

(b) Discuss the use of the sample variance s2 with positively autocorrelated data. Specifically, if the observations at lag i have autocorrelation i, is s2 still an unbiased estimator for 2?

(c) Does your answer in part (b) imply that s2 would really be a good way (in practice) to estimate 2 in constructing a control chart for autocorrelated data?

**View Solution:**## Answer to relevant Questions

The viscosity of a chemical product is read every two minutes. Some data from this process are shown in Table 10E.11 (read down, the across from left to right). (a) Is there a serious problem with autocorrelation in these ...An x chart is used to maintain current control of a process. The cost parameters are a1 = $2, a2 = $0.50, a3 = $50, a′3 = $75, and a4 = $200. A single assignable cause of magnitude δ = 1 occurs, and the duration of the ...A sample of five units is taken from a process every half hour. It is known that the process standard deviation is in control with σ = 2.0. The x values for the last 20 samples are shown in Table 10E.7. Specifications on ...Suppose that there are p = 4 quality characteristics, and in correlation form all four variables have variance unity and that all pairwise correlation coefficients are 0.9. The in-control value of the process mean vector ...Reconsider the situation in Exercise 11.2. Suppose that the sample mean vector and sample covariance matrix provided were the actual population parameters. What control limit would be appropriate for phase II of the control ...Post your question