Quality Control and Acceptance Sampling

8/7/2019 Quality Control and Acceptance Sampling

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Quality Control andQuality Control and

Acceptance SamplingAcceptance Sampling

Oller, Mark Angelo O. L.

BSBA Management

Production & Operations Mgt.


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Purpose of Quality Control:

- T o assure that processes are performing in an acceptable manner

Quality Control

-A process that evaluates output relative to a standard, and takescorrective action when output doesnt meet standards. If the results are

acceptable, no further action is required; unacceptable results call for

corrective action


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Quality Control Techniques

can be applied to an organizations inputs, transformation system, andoutputs

Acceptance Sampling

quality control applied to inputs and outputs

Process Control

quality control applied to the transformation system


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INSPECTION

Is an appraisal activity that compares goods or services to a standard

Involves determining, sometimes by testing, whether or not an input or

output conforms to organizational standards of quality

it occur at three points:

1.Before production the logic of checking conformance is to make surethat inputs are acceptable

2.During production the logic of checking conformance is to make sure

that the conversion of inputs into output is proceeding in an acceptablemanner

3.After production the logic of checking conformance is to make a finalverification of conformance before passing goods on to customers.


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Inspection before and after production often involves ACCEPTANCE

SAMPLING procedure; monitoring during the production process is referred

to as PROCESS CONTROL

INPUTS TRANFORMATION OUTPUTS

Acceptance Sampling - Process Control - Acceptance Sampling

Where to Inspect in the Process?

1.UPON RECEIPT OF RESOURCES checking the quality of raw materials

and purchased parts and supplies, testing equipment for ability to meetspecifications, verifying the skills of the staff


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2.BEFORE TRANSFORMATIONOPERATIONS BY THE WORKER if anoperation is expensive, irreversible (such as mixing food ingredients), or

of a concealing nature (such as assemblies, coating, plating)

3. IMMEDIATELYBEFORE ANYBOTTLENECKOPERATION

there is no advantage in feeding a scarce resource defective items thatsimply consume more of its time

4.WHEN THE FIRST FEW ITEMS COME OUT OF AN AUTOMATIC OPERATION

5.AFTER TRANSFORMATIONOPERATIONS

6.INFINDINSPECTION

7.WHEN CUSTOMERS COMPLAIN, RETURN GOODS,OR REQUIRE SERVICE


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Example of inspection points in service organization:

Types ofBusiness Inspection Points Characteristic

Fast food -Cashier Accuracy

-Counter Area Appearance, Productivity

-Eating Area Cleanliness, No loitering

-Building & Ground Appearance,S afety

Hazards

-Kitchen Cleanliness, Purity of

food, Food storage,

Health Regulations


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Quality of Conformance

a product or service conforms to specifications

Statistical Process Control

to evaluate the output of a process to determine if it is statisticallyacceptable

Control Chart

A statistical tool used to distinguish between variation in a processresulting from common causes and variation resulting from special causes.

It presents a graphic display of process stability over time.


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Purpose of Control Chart:

To monitor process output to see if it is random

To monitor the extent to which our products meet specifications. In the

most general terms, there are two "enemies" of product quality:

1. deviations from target specifications

2. excessive variability around target specifications

How do we develop a control chart?

Developing a control chart consists of four major steps:

Step 1: Determine what to measure

Step 2: Collect the data

Step 3: Plot the data

Step 4: Calculate the control limits


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Variable Data

are measurable characteristic such as weight, temperature, anddiameter.

Attribute Data

are descriptive characteristic of an output such as acceptable and

defective or good and bad.

Chance Variation(Random)

is the variability that is built into (actually, allowed to remain in) the

system. There is a play between the gears and mechanical parts of

machines; there is variation in the inputs; processing conditions are

variable; and human performance is particularly variable.


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Assignable Variation

occurs because some element of the system or some operating conditionis out of control. A machine may be excessively worn, a part may be

broken, a worker may be mistrained, inspection gages or instruments

may be faulty, and so forth.

Two types of Errors:1. Type I error is committed when an innocent defendant (a good-

quality lot) is found guilty (declared defective)

2. Type II error is made when a guilty defendant (a defective lot) is

found innocent(declared of good quality)


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Variables generate data that are measured

Attributes generates data that are counted

Mean Control Chart control chart used to monitor the central tendencyof a process

Range Control Chart control chart used to monitor process dispersion

p-Chart control chart for attributes, used to monitor the proportion ofdefective items in a process

c-Chart control chart for attributes, used to monitor the number ofdefects per unit


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Run Test

a test for randomness

Run

sequence of observation with a certain characteristics

Specifications a range of acceptable values established by engineering design or

customer requirements

Process Variability

natural or inherent variability in a process

Process Capability

the inherent variability of process output relative to the variation

allowed by the design specification


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Acceptance Sampling

Acceptance Sampling form of inspection applied to lots or batches of

items before or after a process, to judge conformance with predetermined

standards

Sampling Plans plans that specify lot size, sample size, number of

samples, and acceptance/rejection criteria

Single-Sampling Plan one random is drawn from each lot and every item

in the sample is examined and classified as either good or defective.

Double-Sampling Plan allows for a opportunity to take a second sampleif the results of the initial sample are inconclusive

Multiple-Sampling Plan similar to a double-sampling pan except that

more than two samples may be required

Documents

Quality Control and Acceptance Sampling