This presentation will help to understand basics of Attribute measurement analysis, its importance and application

2. ◦ Introduce the basic concepts of an attribute
measurement systems analysis (MSA).
◦ Understand operational definitions for inspection and
evaluation.
◦ Define attribute MSA terms.
◦ Define Procedure for conducting attribute MSA
◦ Demonstrate trial for conducting attribute MSA
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3.  A measurement systems analysis is an evaluation
of the efficacy of a measurement system.
 The purpose of Measurement System Analysis is
to qualify a measurement system for use by
quantifying its accuracy, precision, and stability.
 It is applicable to both continuous and attribute
data.

5.  Most problematic
measurement system
issues come from
measuring attribute data
in terms that rely on
human judgment such
as good/bad, pass/fail,
etc. This is because it is
very difficult for all
testers to apply the same
operational definition of
what is “good” and what
is “bad.”

6.  When, we are not getting any measurement values then
the tool used for this kind of analysis is called Attribute
gage R&R.
 The R&R stands for repeatability and reproducibility.
 Repeatability : is the variation in measurements obtained
with one measurement instrument when used several
times by one appraiser while measuring the identical
characteristic on the same part.
 Reproducibility : It is defined as the variation in the
average of the measurements made by different
appraisers using the same measuring instrument when
measuring the identical characteristic on the same part.
 .

7.  To evaluate product features and make
accept/reject decisions.
 • Mandatory criteria for establishment and
use of operational definitions include:
 A) Criteria that can be applied to an object
(or a group of objects) which precisely
describes what is acceptable and
unacceptable.
 B) A written description of the process for
collecting data, including the method in
which accept/reject decisions will be made.
 C) Review of the accept/reject criteria
with people who will do the inspections to
ensure that the requirements are
understood.

8.  Select at least 20 parts to be evaluated during the study.
 • At least 5 of the parts should be defective in some way. If larger
sample sizes are used, include at least 25% defective parts.
 • Care should be taken when selecting defective parts – If possible
select parts which are slightly beyond the specification limits or
acceptance standards. Label each part with proper identification.
 • Three inspectors will evaluate each part thrice (Three trials).
 • A fourth person should record the data. Note down the observations
in the form of 1 or 0, 1 is OK, 0 is not ok.
 The order of inspections should be randomized after each group of
inspections to minimize the risk that the inspector will remember
previous accept/reject decisions. The inspectors must work
independently and cannot discuss their accept/reject decisions with
each other.

9. Appraiser A A A B B B C C C
Trials i ii iii i ii iii i ii iii
1 1 1 1 1 1 1 1 1 1
2 1 1 1 1 1 1 1 1 1
3 1 1 1 1 1 1 1 1 1
4 0 0 0 0 0 0 0 0 0
5 1 1 1 1 1 1 1 1 1
6 1 1 1 1 1 1 1 1 1
7 1 1 1 1 1 1 1 1 1
8 1 1 1 1 1 1 1 1 1
9 1 1 1 1 1 1 1 1 1
10 1 1 1 1 1 1 1 1 1
11 1 1 1 1 1 1 1 1 1
12 1 1 1 1 1 1 1 1 1
13 1 1 1 1 1 1 1 1 1
14 1 1 1 1 1 1 1 1 1
15 1 1 1 1 1 1 1 1 1
16 1 1 1 1 1 1 1 1 1
17 1 1 1 1 1 1 1 1 1
18 1 1 1 1 1 1 1 1 1
19 1 1 1 1 1 1 1 1 1
20 1 1 1 1 1 1 1 1 1
• The data recorder may use a table similar to the one given below.
0 Not Ok
1 Ok

10.  • Type 1 Errors: when a good part is rejected.
 • Type 1 errors increase ‐
 • Manufacturing costs. Incremental labor and material expenses
are necessary to re – inspect, repair, or dispose the suspect parts.
 • Type 1 errors are also called as “Producer’s Risk” or alpha
errors.
 • Type 2 Errors: when a bad part is accepted.
 • Type 2 errors may occur
 • Perhaps the inspector was poorly trained or rushed through the
inspection and inadvertently overlooked a Small defect on the
part.
 • When Type 2 errors occur, defects slip through the containment
net and are shipped to the customer.
 • Because Type 2 errors put the customer at risk of receiving
defective parts; customer may raised the complaint!
 • Type 2 errors are sometimes called as “Consumer’s Risk”.
 • Type 2 errors are also called as “beta” errors.

11. What is effectiveness?
The effectiveness of an inspection process is correct
call!
◦ Correct Call (Cc):- The number of times of
which the operator (s) identify a good sample
as a good one.
Effectiveness = number of correct evaluations
number of total opportunities

12. What is False Alarm?
 False Alarm (Fa) – The number of times of
which the operator (s) identify a good sample
as a bad one.
The probability of a false alarm, also known as
Type I error or producer’s risk, is given by:
Fa (False Alarm) = number of false alarms
number of non-defective items

13. What is Miss rate?
A miss is a defective item that is classified as non-
defective.
Miss rate (Mr) – The number of times of which
the operators identify a bad sample as a good
one.
The probability of a miss, also known as Type II
error or consumer’s risk, is given by:
Mr (Miss rate) = number of misses
number of defective items

14.  Acceptability criteria:
If all measurement results agree, the gage is
acceptable. If the measurement results do not
agree, the gage can not be accepted, it must be
improved and re-evaluated.
EFFECTIVENESS (< 80% - Not Acceptable)
MISS - RATE ( > 5% - Not Acceptable )
FALSE ALARM RATE( > 10% -Not Acceptable)

15.  What could have caused the poor agreement?
 What should be done to improve the measurement
system?
 What should be done to improve consistency?
 Do the Brain
Storming!

16.  If any of the decisions disagree, the
measurement system may need improvement.
 Improvement actions include:
 • Reworking the gage,
 • Re‐training the inspectors,
 • Clarifying the accept/reject criteria,
 • Adding more lighting
 After implementing the improvement actions,
repeat the study. If the error cannot be
eliminated,
 • Must take appropriate corrective actions, such
as switching to a new measurement system,
adding redundant inspections, or conducting a
more extensive study.

17. Exercise