Accuracy refers to how close a measured value is to the actual or true value, while precision refers to the reproducibility of measurements and how close repeated measurements are to each other. Accuracy depends on simple analysis techniques and can be improved, whereas precision depends on many factors and sophisticated techniques and cannot be improved. Precision is necessary for accuracy but accuracy is not sufficient for precision. Factors that can affect precision and accuracy include standards, workpieces, instruments, persons performing measurements, and environmental conditions like temperature, pressure, and vibrations.

1. ACCURACY VS PRECISION
 ACCURACY IS HOW CLOSE A
MEASURED VALUE IS TO THE
ACTUAL (TRUE) VALUE .
 IT IS CLOSENESS WITH THE TRUE
VALUE OF THE QUANTITY BEING
MEASURED.
 PRECISION IS HOW CLOSE THE
MEASURED VALUES ARE TO EACH
OTHER.
 IT IS A MEASURE OF THE
REPRODUCIBILITY OF THE
MEASUREMENT.

2. ACCURACY V/S PRECISION

3. ACCURACY VS PRECISION
# ACCURACY PRECISION
1 It is closeness with the true value of the
being measured.
It is a measure of the reproducibility of the
2 The accuracy of the measurement means
conformity to truth.
The term precise means clarity or sharply defined.
3 Accuracy can be improved. Precision cannot be improved.
4 Accuracy depends upons simple techniques of
analysis.
Precision depends upon many factors and required
sophisticated techniques 0of analysis.
5 Accuracy is necessary but not sufficient
for precision.
Precision is necessary but not sufficient condition for
accuracy.

4. FACTOR AFFECTING PRECISION AND ACCURACY
S STANDARD
W WORKPIECE
I INSTRUMENTS
P Person
E ENVIRONMENTS

5. 1. STANDARD
Normally the measuring instruments is calibrated
with a standard are at regular intervals. The standard
may be affected by
 Coefficient of thermal expansion
 Stability with time
 Elastic properties'
 Geometric compatibility
 Positions etc.

6. 2. WORKPIECE
The following factors affects the accuracy
 Cleanliness surface finish etc.
 Surface Defects
 Hidden geometry
 Thermal equalization etc.

7. 3. Instruments
The inherent characteristics of the instruments which affect the accuracy and
precision are
 Inadequate amplification
 Scale error
 Effect of friction backlash hysteresis etc.
 Deformation while handling heavy workpiece
 Calibration error
 Repeatability & readability

8. 4. PERSON
The factors responsible for accuracy are
 Training skill
 Sense of precision appreciation
 Ability to select measuring instruments & standards
 Attitude towards personal accuracy achievement
 Planning for measurement techniques to have minimum just with
consistent in precision.

9. 5. ENVIRONMENTS
The environments factors are
 Temperature , Pressure , Humidity
 Clean Surroundings and minimum vibrations
 Adequate illumination
 Temperature equalization between standards workpiece and instruments.

10. Thanks
you.