Question

Statistical process control
explain the types of control charts available for analysis, the basis under which their limits are defined and change, the types of analysis that lead to decisions of controlled or not-controlled, and the types of risks associated with different sample sizes and limit settings. In particular, describe what it means statistically to declare that a process is not in control.

Answer 1

Types of control charts for analysis would be as followed:

Limits of each chart is within +3σ and -3σ, within these limits the following would be:

UCL (upper control limit)- seprately calculated for each chart (certainly depend on the type of the chart)

LCL (lower control limit) -seprately calculated for each chart (certainly depend on the type of the chart)

CL (Central line) - divides the chart into two equal parts.

If the data points under the charts, we have to find the UCL and LCL and if points are within UCL and LCL then statistically are process is in control. If any data point outside these limits then that point are not within limits and process is not under control we have to eliminate that point and then do the calculation again to find out that process is under control or not.

Risks associated are as followed:

1) Type 1 error- Also known as the producers risk that quality of product is good still rejected by consumer as bad product.

2) Type 2 error- Also known as the consumers risk that quality of product is not so good still pass the quality test by the manufacturer's quality test.