Accuracy and Precision


okay let us start

the other areas of analytical chemistry

analytical chemistry qualitative



what is the difference between accuracy

and precisions

value the average of the best

results obtained by efficient and

experienced workers

in many laboratories using

different techniques or those obtained

by using the most

highly sophisticated instruments is the


probable value generally taken as the

true value above


between the result observed value

and the true value or most probable


precision and angular concordance of a

series of measurements of the

same quantity

law it represents how close the

measurements are to

each other

for example




the difference between the true value

and the measured value of

a quantity is known as error and either


in the value and that is



first one absolute error second one

relative error

it is the difference between the

observed value and the

true value that is absolute error

is x observed minus x

t where x obs

meaning observed value and x

t means true value


next one is relative error it is the

ratio of the error to the

true or most probable value

it is usually represented

x observed minus x t divided by

x t into hundred percentage

the percentage then

parts per thousand dollar er


operational and personal error then

method error instrumental and reagent


fourth one additive and proportional


indeterminate errors classifies



can be avoided or its magnitude can be

determined these errors can either be

eliminated or improved by repetition

determination first of all not in the

operational error

another one misinterpreting directions

with respect to conditions such as

temperature ph

experiment conditions temperature ph

conditions now other misinterpreted

next one is instrumental and reagent


it is due to the use of defective


or by using defective apparatus such as

balance weight glassware etc

the instrumental error is so useful

for the number

properly in accordance with the

requirement or one which attacks



such errors may arise from incorrect


incompleteness of reactions


analysis it arises due to side reactions

non-stoichiometry of the reaction etc

either number of volumetric analysis s



are independent of the amount of

constituent present

in determination

an example on a in weight of a crucible

in which precipitate is ignited or due

to errors

in weight etc

analysis precipitate crucible vegetable


error depends upon the amount of

constituent present in

determinations example

presence of impurity in standard


weight and hence the molarity of

solution prepared

either number one substance usage

solution preparing


whose magnitude cannot be determined

these are a group of unsuspected and

non-reproducible errors otherwise

these errors are beyond the control of



due to the inability of the analyst to

distinguish between slightly different

readings colors position in needles etc

this cannot be corrected by a repetition

of the experiment because the inherent