PROCESS significant manner, the tests also reflects on

PROCESS
QUALITY ENGINEERING

MEASUREMENT SYSTEM AND ANALYSIS

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ASSIGNMENT – 1

on

BIAS

 

 

Submitted
by

SRINATH
THANGARAJRAJA

8151813

 

 

EXECUTIVE SUMMARY:

In this report, we are taking length
of an ignition tube to find whether the observation values are biased or not,
and the report is made by the values observed during the observation and the bias
value is found using the formulas in excel and graph from Minitab which are
shown to give clear results.

REPORT:

Example:

 

As a quality assurance engineer I was evaluating the
observations of the product and analysis of the measurement equipment indicated
that there should be no linearity concerns, so I had only the bias of the
measurement system evaluated. I took the measurement of the length of an ignition
tube in the motor bike which was measured by Vernier calliper in (mm)The
part was measured with reference to layout inspection to determine its
reference value. and was then measured 10 times to see the bias values.  And the values of t statics and t critics are
found with standard deviation and standards error of the mean using the
observed value in excel.

Reference value =19.920

Trial

Observed
Value(mm)

Bias(mm)

1

20.7521

0.8321

2

20.8523

0.9323

3

20.7563

0.8363

4

19.999

0.079

5

20.9214

1.0014

6

19.8923

-0.0277

7

20.7991

0.8791

8

19.9976

0.0776

9

20.4464

0.5264

10

19.9812

0.0612

 

 

 

n

Average 

Standard
Deviation,

Standard Error of Mean, b

Measured Value

10

20.4397

0.4254

0.1345

 

 

 

 

 

Reference
Value = 19.920     ?
=.05

 t 
statistic

 
df

 
Significant t value (2-tailed)

 
Average Bias

Confidence Interval of the Bias

Lower

Upper

Measured
Value

3.863

9

     
2.14479  

0.519

0.2154

0.824

 

GRAPHS FROM MINITAB:

`

 

 

 

                                                       

 

 

 

Conclusion & result:

From these graphs the value shows us that’s
the zero falls within the interval of bias so that I can assume that the
measurement bias is acceptable assuming no need of additional variation. And
more over all the values are lesser than t-critic value showing us the product
falls under the rejection category. SO, the
system is biased, and if the measurement has to be non-zero bias it
possibly should be recalibrated to achieve zero bias or the instrument should
have been worn out which should be maintained. The bias study is performed to
verify whether the instrument is measuring offset in a significant manner, the
tests also reflects on the calibration state of instruments and establish the suitability
of instruments to measure the process, the bias study should also be performed
when the instrument is initiated into a new process.

 

The calculations of the standard
deviation, standard error of the mean, average bias, lower limit and upper
limit are done in excel worksheets which are attached with this assignment.