# Figures of Merit

- Page ID
- 279969

Figures of merit are a way for analytical chemists to characterize a method. The six figures of merit we will use are precision, accuracy, sensitivity, linear dynamic range, detection limit, and selectivity.

In order to complete this exercise, first download the “InClass 2 Figures of Merit” Excel file from Canvas. It is the In-Class Assignments Module.

Learning Objectives

After completing this exercise, students will be able to:

- Calculate the standard deviation and confidence interval for a data set.
- Describe the precision of a data set.
- Describe the accuracy of a data set.
- Estimate the sensitivity and linear dynamic range from a calibration curve.
- Calculate the detection limit and limit of quantitation from a data set.

- Using the data on the Precision and Accuracy tab, calculate the average, standard deviation, percent relative standard deviation, and 95% confidence interval.
- What is the precision of the data?
- The known value for the data is 0.1500. Is there evidence of bias? Support your answer.

- A calibration curve is presented in the Calibration Curve tab, where the response of a method is plotted versus the analyte concentration.
- Estimate the linear region of the data. One way to approach this problem is to selectively remove data points from the plot until you maximize the R
^{2}value. If you do not know how to do this, I will be happy to show you. - What is the sensitivity in the linear region? Note – sensitivity has units.

- Estimate the linear region of the data. One way to approach this problem is to selectively remove data points from the plot until you maximize the R

- Data are presented in the Limit of Detection tab for 10 replicate measurements of a 4.00 mM sample ([A] = 4.00 mM) and 10 replicate measurements of a blank ([A] = 0 mM). Perform the following calculations in the spreadsheet. Use the calibration curve from part (2) to determine the slope.
- Calculate the signal detection limit.
- Calculate the limit of detection.
- Calculate the signal quantitation limit.
- Calculate the limit of quantitation.

Submit the completed Excel spreadsheet through Canvas. Answer all questions directly on the Excel spreadsheet.

## Contributors and Attributions

- Susan Oxley, St. Mary’s University (San Antonio) (soxley@stmarytx.edu)
- Sourced from the Analytical Sciences Digital Library