uncertainity and precision?

[bilquees]

wts the difference b/w uncertainity and precision?

 

[Mufaddal]

Least Count/Precision

Minimum reading of an instrument which it can record.
Eg.
Meter rule - 1mm
Micrometer screw gauge - 0.01mm
Vernier caliber - 0.1mm or 0.02mm or 0.05mm
*You have to know the above values, except for the vernier caliber one which i think will be mentioned in the question.

Uncertainty

Uncertainty is not an error. It is the inability of an instrument to record more accurate values. Uncertainty of an instrument is equal to its least count. Uncertainty of an analogue instrument is equal to half the least count. Therefore, uncertainty of meter rule is equal to 0.5mm. But when measurements are taken by using meter rule, 2 readings are recorded. One is at zero level and the other is the final reading. Each of the readings have an uncertainty of 0.5mm. Therefore, uncertainty of meter rule measurement is 1mm.

Percentage certainty of a single measurement.

% uncertainty is equal to uncertainty over the measurement times 100

Random error

Inability of the instrument or the experimenter to record the same measurement when the same experiment is repeated. Random error can be reduced through repeated readings.

Systematic error

This is due to the defect of the instrument or the mistake in the method. Systematic error cannot be reduced by repeated measurements. Error correction should be done or instrument has to be replaced.

Eg. Repeated measurement of X1, X2, X3, X4 are taken.

Uncertainty is equal to half times the difference of the maximum measurement and the minimum measurement.
So in this case if X5 is max and X1 is min

the uncertainty is equal to 1/2(X5-X1)

% uncertainty = (1/2(X5-X1)) / (average value) * 100

NOTE Eg. If readings 0.23,0.21,0.25,0.24,0.08 , when asked for average don't add 0.08

 

[bilquees]

thank u

 

[Hamzeh S]

Least Count/Precision

Minimum reading of an instrument which it can record.
Eg.
Meter rule - 1mm
Micrometer screw gauge - 0.01mm
Vernier caliber - 0.1mm or 0.02mm or 0.05mm
*You have to know the above values, except for the vernier caliber one which i think will be mentioned in the question.

Uncertainty

Uncertainty is not an error. It is the inability of an instrument to record more accurate values. Uncertainty of an instrument is equal to its least count. Uncertainty of an analogue instrument is equal to half the least count. Therefore, uncertainty of meter rule is equal to 0.5mm. But when measurements are taken by using meter rule, 2 readings are recorded. One is at zero level and the other is the final reading. Each of the readings have an uncertainty of 0.5mm. Therefore, uncertainty of meter rule measurement is 1mm.

Percentage certainty of a single measurement.

% uncertainty is equal to uncertainty over the measurement times 100

Random error

Inability of the instrument or the experimenter to record the same measurement when the same experiment is repeated. Random error can be reduced through repeated readings.

Systematic error

This is due to the defect of the instrument or the mistake in the method. Systematic error cannot be reduced by repeated measurements. Error correction should be done or instrument has to be replaced.

Eg. Repeated measurement of X1, X2, X3, X4 are taken.

Uncertainty is equal to half times the difference of the maximum measurement and the minimum measurement.
So in this case if X5 is max and X1 is min

the uncertainty is equal to 1/2(X5-X1)

% uncertainty = (1/2(X5-X1)) / (average value) * 100

NOTE Eg. If readings 0.23,0.21,0.25,0.24,0.08 , when asked for average don't add 0.08

so the uncertinity of a meter rule is 0.5 or 1?

and the graph detects random or systematic error ?