1. Chapter 3: Measurement: Accuracy, Precision, and Error

2. Objectives
Distinguish among accuracy, precision, and error of a measurement

3. Measurements Measurement quantity that has both a number and a unit
fundamental to experimental science so must be able take and evaluate them

4. Evaluating measurements
Accuracy
measure of how close a measurement comes to the actual or true value of whatever is measured.
Precision
measure of how close a series of measurements are to one another.

5. Evaluating measurements
Accuracy vs. Precision

6. Evaluating measurements

7. Evaluating measurements
Often, we are experimentally determining a value in the lab that is already known.
When we do this, we must calculate error in order to see how accurate and precise our results are
In lab reports, you will be required to determine your error and percent error.

8. Evaluating measurements
To determine Error:
The accepted value is the correct value based on reliable references.
The experimental value is the value measured in the lab.
The difference between the experimental value and the accepted value is called the error. .

9. Evaluating measurements
To determine Percent Error:
The percent error is the absolute value of the error divided by the accepted value, multiplied by 100%. .

10. Practice: error and percent error
Question 1
The accepted value for the boiling point of water is 100.0°C. In the lab, you experimentally determined it to be 98.7°C. What is the error and percent error?

11. Practice: error and percent error
Answer 1
Given
Accepted value = 100.0°C
Experimental value = 98.7°C
Work .
Error = 98.7°C °C = °C