Question

in Analytical chemistry laboratory. Nickle(ppm)in water sample estimated by two different students was as ,student 1 (25 24 24 24 24 28 26 ) and student 2 (24 25 24 24 25 25 ), if the true valude on Nickle in water was 20 ppm estimate the precision and accuracy of both students

Answer 1

Answers are in the explanation

Step-by-step explanation:

Precision and accuracy are both statistical concepts. Precision is about how close are the measured values to each other. Accuracy is closeness of the measured values to a specific value or reference value.

There are many ways to calculate precision and accuracy, one is stimating precision as Relative Uncertainty and accuracy as Relative Error.

Formulas are:

Relative Uncertainty: Standard desviation / Measured value.

Relative Error: Measured Value - Expected Value / Expected value

Measured value is the aveage of the values.

For student 1:

Mean = 25

Standard desviation = 1.5275

Relative Uncertainty: 1.5275 / 25

Relative Uncertainty: 0.061

Relative Error: 25 - 20 / 20

Relative Error: 0.25

For student 2:

Mean = 24.5

Standard desviation = 0.5477

Relative Uncertainty: 0.5477 / 24.5

Relative Uncertainty: 0.02

Relative Error: 24.5 - 20 / 20

Relative Error: 0.225

As the student 2 has a low Relative error and uncertainty, you can say student 2 is more accurate and precise