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Quality Control > M2 STATISTICAL QUALITY CONTROL > Flashcards

M2 STATISTICAL QUALITY CONTROL Flashcards

1
Q

identified portion of a batch having uniform character and quality within specified limits

A

Lot/Batch

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2
Q

representative/portion

A

Sample

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3
Q

Look at all 5,000 shells

A

100% inspection

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4
Q

Don’t look at any, put the whole shipment into stock

A

0% inspection

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5
Q

Look at some of them, and if enough of those are good, keep the lot

A

Acceptance sampling

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6
Q

status

A

Lot disposition

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7
Q

decision

A

Lot sentencing

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8
Q
  • Testing is destructive
  • Cost of 100% inspection is high
  • 100% inspection is not feasible
    (require too much time)
  • If vendor has excellent quality history
    8
    Statistical Quality Control
A

Why Acceptance Sampling and Not 100% Inspection

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9
Q
  • Less expensive
  • Reduced damage
  • Reduces the amount of inspection error
A

Advantages of Sampling

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10
Q
  • Risk of
    – accepting “bad” lots
  • Consumer’s Risk
    – rejecting “good” lots
  • Producer’s Risk
  • Less information generated
  • Requires planning and documentation
A

Disadvantages of Sampling

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11
Q

accepting “bad” lots

A

Consumer’s Risk

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12
Q

rejecting “good” lots

A

Producer’s Risk

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13
Q

Indicated the number of units of product from each lot or batch which are to be inspected (sample size or series of sample sizes) and the criteria for determining the acceptability of the lot or batch (acceptance and rejection numbers)

A

Sampling Plan

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14
Q

The units selected for inspection should be chosen at “random.”

A

Random Sampling

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15
Q

unbiased

A

Random Sampling

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16
Q

When we took the capsule shell sample, we didn’t put them back into the lot during sampling, i.e., we didn’t replace them.

A

Sampling with/without Replacement

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17
Q

acceptance sampling

A

we sample without replacement

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18
Q

each piece in the lot has equal probability of being in the sample

A

simple random sample

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19
Q

he lot is divided into ‘H’ groups, called “strata.”

Each item in the lot is in one and only one stratum

A

stratified sample

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20
Q

Sampling plans are typically set up with reference to–

A

Acceptable Quality Level (AQL)

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21
Q

is the base line requirement for the quality of the producer’s product

A

Acceptable Quality Level (AQL)

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22
Q

– the poorest level of quality (percent nonconforming) that the process can tolerate

A

Acceptable Quality Level (AQL)

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23
Q

Scenario:
– N = 100 products
– AQL = 10% (max. 10 defectives allowed)
– If no. of defectives < 10 → Accept
– If no. of defectives > 10 → Reject

A

Acceptable Quality Level (AQL)

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24
Q

Scenario:
– N = 100 products
– AQL = 5% (max. 5 defectives allowed)
– If no. of defectives < 5 → Accept
– If no. of defectives > 5 → Reject

A

Acceptable Quality Level (AQL)

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25
Q

Which one has higher standard of quality in the production process?

Higher or lower AQL??

A

Lower

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26
Q
  • Used to measure acceptable levels of quality of the products inspected
  • Widely used to decide whether to accept a production lot without checking every single item.
A

MIL-STD-105E

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27
Q

– The most recently published version is MIL-STD-105E

  • Notice 1 cancelled the standard and
    refers DoD users to ANSI/ASQC Z1.4-1993
A

MIL-STD-105

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28
Q

AQL and defect classification Defects detected during inspections are generally classified in 3 categories

A
  • Critical defect
  • Major defect
  • Minor defect
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29
Q

An undesirable characteristics of a product

A

Defects

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30
Q

is a unit of a product which contains one or more defects

A

DEFECTIVE

31
Q

Classification of Defects
* According to Seriousness or Gravity

A
  • Critical defect
  • Major defect
  • Minor defect
32
Q

can endanger life or property, may render the product non-functional

A

Critical Defect

33
Q

renders the product useless

A

Major Defect

34
Q

slight variations

A

Minor Defect

35
Q

Classification of Defects

  • According to Measurability
A

–Variable Defect
–Attribute Defect

36
Q

single, measurable quality characteristic

A

Variable Defect

37
Q
  • Not represented numerically
  • Defective or non-defective
  • Conforming or Non-conforming
A

Attribute Defect

38
Q

Classification of Defects

  • According to Nature
A

–Ocular Defect - visible
– Internal Defect – not seen but present
–Performance Defect - function

39
Q

Variations

– Cannot be identified and unavoidable
– Common and inherent on the process
– Cause slight differences in process variables like diameter, weight, service time, temperature, etc.

A

Random

39
Q

Variations

– Assignable
– Causes can be identified and eliminated
– Typical causes are poor employee training, worn tool, machine needing repair, etc.

A

Non-random

40
Q

(Assessing the Quality of Results)

A

Statistics

40
Q

Sources of Variations

– Variation between supplies of same substance
– Between batches from same supplier
– Within a batch

A

Materials

41
Q

Sources of Variations

– Variation of equipment for the same process
– Differences adjustment of equipment
– Aging and improper care

A

Machines

42
Q

Sources of Variations

– Inexact procedures
– Inadequate processes
– Negligence by chance

A

Methods

42
Q

Sources of Variations

– Improper working conditions
– Inadequate training and understanding
– Dishonesty, fatigue and carelessness

A

Men

42
Q
  • It is impossible to perform analysis without any error or uncertainties.
  • The TRUE value of a measurement is never known exactly.
  • Replicates are samples of the same size that are analyzed in exactly the same way.
A

Statistics

43
Q

The TRUE value of a measurement is

A

never known exactly

43
Q

are samples of the same size that are analyzed in exactly the same way.

A

Replicates

44
Q

It is impossible to perform analysis without any

A

error or uncertainties

45
Q

(Average)

A

Mean

46
Q

central or “best” value

A

Mean and median

46
Q

(middle result when arrange in order)
– Odd numbered samples → the middle
– Even numbered samples → average of the middle pair

A

Median

47
Q

– Closeness of measurements with each other
– Reproducibility of measurements

A

PRECISION

48
Q

– STANDARD DEVIATION
(s or SD)
* The higher the s, the less precise the measurements are.
– VARIANCE (s2)
– COEFFICIENT OF VARIANCE (CV)
– RANGE (SPREAD)

A

PRECISION

48
Q

– Closeness of measurement to its TRUE (accepted) value

A

ACCURACY

48
Q
  • Composed of:
    – Central Line
    – Upper Line for the UCL
    – Lower Line for the LCL
  • Can conclude if variation is
    – CONSISTENT (in-control)
    – UNPREDICTABLE (out of control)
A

Control Charts

49
Q

– ERROR
* ABSOLUTE ERROR
* RELATIVE ERROR

A

ACCURACY

49
Q
  • means of visualizing variations that occur in the central tendency and dispersion of a set of observations
  • used to study how a process changes over time
A

CONTROL CHARTS

50
Q

TYPES OF CONTROL CHARTS

A
  • ATTRIBUTES
    – p-chart
    – c- chart
  • VARIABLES
    – X-chart
    – R-chart
50
Q

– X-chart
– R-chart

A

VARIABLES

50
Q
  • Determine the mean, UCL and LCL.
  • Estimate an arbitrary range (with same interval).
  • Draw the lines.
  • Plot the data.
    – Number of sample (X-axis)
    – Sample Weight (Y-axis)
  • Interpret the results.
    – Out-of-control signals
A

Construct a Control Chart

50
Q

– p-chart
– c- chart

A

ATTRIBUTES

51
Q

establishes a high degree of certainty

A

Validation

52
Q

Validation Parameters

A
  • Accuracy
  • Precision
  • Selectivity
  • Linearity
  • Range
  • Sensitivity
  • LOD
  • LOQ
  • Ruggedness
  • Robustness
52
Q

– Measure of exactness

A

Accuracy

52
Q

Measure of degree of “reproducibility/repeatability” under [normal] condition

A

Precision

53
Q

– Ability to measure the analyte of interest

A

Selectivity/Specificity

54
Q

Ability to produce results that are directly proportional to concentration of analyte

A

Linearity

55
Q

Lowest concentration of analyte that can be detected/measured

A

Limit of Detection (LOD) / Limit of Quantification (LOQ)

55
Q

Highest and lowest level of analyte that can be measured

A

Range

56
Q

Degree of reproducibility under variety of test conditions

A

Ruggedness

57
Q

– Ability to remain unaffected by small variations

A

Robustness

57
Q

– Ability to record small variations (changes)

A

Sensitivity

58
Q

Meaning of MIL-STD

A

Military Standard

Quality Control (4 decks)

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