Dr. Bincy Joseph from St. Mary's College in Thrissur discusses types of errors in analytical measurements. There are two main types of errors - systematic errors which are reproducible and can be identified and corrected, and random errors which are unpredictable. Systematic errors include instrumental errors from faulty calibration, method errors from non-ideal chemical behavior, and personal errors from human judgment. Random errors have no identifiable cause and set an ultimate limit to measurement precision. Accuracy refers to closeness to the true value, while precision refers to the agreement between multiple measurements of the same quantity. Proper calibration, experimental technique, and replicate measurements can improve accuracy and precision.

1. ERRORS
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur
1
Dr Bincy Joseph
ASSISTANT PROFESSOR
DEPARTMENT OF CHEMISTRY
ST. MARY’S COLLEGE, THRISSUR

2. Errors
 The numerical difference between
a measured value and the absolute
or true value of an analytical
determination.
 The error in a measured quantity
may be represented either as
absolute error or as relative error.
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur 2

3. 1.Absolute error(E)
E=Xi-Xt
Xi=measured value
Xt=true value
2. Relative error (Er)
Er=(Xi-Xt/Xt) 100 %
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur 3

4. Types of Errors
No analysis is free of error or “uncertainty”
1.Systematic Error (determinate error)
The error is reproducible and can be discovered
and corrected.
2.Random Error (indeterminate error) Caused by
uncontrollable variables, which can not be
defined/eliminated
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5. Systematic (determinate)
1.Instrumental errors
failure to calibrate, degradation of parts in the
instrument, power fluctuations, variation in temperature,
etc.
Can be corrected by calibration or proper instrumentation
maintenance.
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6. 2. Method errors
- errors due to no ideal physical or chemical
behavior
- completeness and speed of reaction,
interfering side reactions, sampling problems
Can be corrected with proper method
development.
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur 6

7. 3. Personal errors
- occur where measurements require
judgment, result from prejudice, color
acuity problems.
Can be minimized or eliminated with proper
training and experience.
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur 7

8. Correction of Determinant
Errors
 Periodic calibration of the instruments (Instrumental)
 Personal by care and self discipline (Personal errors)
Identification and compensation of method errors by the
following procedures.
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur 8

9. Detection of Systematic Errors
1. Analysis of standard samples
2. Independent Analysis: Analysis using a "Reference Method" or "Reference
Lab"
3. Blank determinations
4. Variation in sample size: detects constant error only.
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10. Random (indeterminate) Error
• No identifiable cause; Always present,
cannot be eliminated;the ultimate
imitation on the determination of a
quantity.
 Eg. reading a scale on an instrument
caused by the finite thickness of the lines
on the scale; electrical noise
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11. Accuracy and Precision:
Accuracy refers to the closeness of a measured value to a standard
or known value.
For example, if in lab one obtain a weight measurement of 3.2 kg for a
given substance, but the actual or known weight is 10 kg, then the
measurement is not accurate. In this case, the measurement is not
close to the known value.
Precision refers to the closeness of two or more measurements to
each other.
Using the example above, if one weigh a given substance five times,
and get 3.2 kg each time, then the measurement is very precise.
Precision is independent of accuracy.
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur 11

12. References
 B.R Puri,L.R Sharma & K C Kalia – Principles of Inorganic
Chemistry
 J D Lee ,Concise Inorganic Chemistry.
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13. THANK YOU
Errors,Dr.Bincy Joseph,St.Marys college,Thrissur 13