Quiz 5 – Process Control and Sustenance

What is the primary purpose of Statistical Process Control (SPC)? *

To eliminate all variation from a process

To distinguish normal process variation from unusual variation and monitor stability

To replace process capability analysis

To determine customer specifications from historical data

Which statement correctly distinguishes control limits from specification limits? *

Control limits are customer requirements; specification limits are calculated from process data

Both limits are calculated from the same historical process data

Control limits describe statistical process behavior; specification limits describe required performance

Specification limits are used only when a process is unstable

A process records one continuous measurement at a time, with no rational subgroups. Which control chart is generally appropriate? *

Xbar-R

Xbar-S

I-MR

Five consecutive continuous measurements are collected as a rational subgroup each hour. Which chart is generally appropriate for small subgroups? *

p chart

Xbar-R chart

u chart

I-MR chart

A company inspects a varying number of units each day and records the proportion that is defective. Which attribute chart is appropriate? *

np chart

c chart

p chart

Xbar-R chart

What does an np chart monitor? *

Number of defects per unit with varying opportunities

Number of defective units when sample size is constant

Process mean for continuous measurements

Moving range of individual measurements

Why is rational subgrouping important in SPC? *

It guarantees that every point will fall inside the control limits

It helps separate short-term within-subgroup variation from variation between subgroups

It eliminates the need for measurement-system analysis

It makes specification limits unnecessary

A control chart shows one point beyond the upper control limit. What is the most appropriate initial response? *

Immediately change the process setting without investigation

Ignore the point because it may still meet specifications

Investigate the process conditions and potential special cause

Recalculate the specification limits

Why should process stability generally be established before capability analysis? *

Capability indices do not require process data

An unstable process may have changing mean or variation, making capability estimates misleading

Control charts can calculate customer specifications

Capability analysis automatically identifies all special causes

Which sequence best represents a practical Control Plan methodology? *

Measure everything, then assign responsibility later

Identify critical characteristics, define requirements and measurement, set monitoring, assign responsibility, and establish a reaction plan

Create specification limits from the control chart and stop monitoring

Use final inspection only and avoid preventive controls

Which statement best describes a reaction plan? *

A list of customer specifications only

A method for calculating Cp and Cpk

Defined actions to take when an abnormal or nonconforming condition is detected

A replacement for standard work

Which example is primarily a preventive control? *

Final inspection of completed products

Weekly audit of completed transactions

An automated validation that prevents submission when a required field is missing

Review of customer complaints after delivery