Estimating process parameters. The x and s control charts for the meshtensioning example (Figures 26.4 and 26.7) were based on = 275 mV and

Estimating process parameters. The x and s control charts for the meshtensioning example (Figures 26.4 and 26.7) were based on μ = 275 mV and

σ = 43 mV. Table 26.1 gives the 20 most recent samples from this process.

(a) Estimate the process μ and σ based on these 20 samples.

(b) Your calculations suggest that the process σ may now be less than 43 mV.

Explain why the s chart in Figure 26.7 (page 26-16) suggests the same conclusion.

(If this pattern continues, we would eventually update the value of

σ used for control limits.)