1. Accuracy & precision
Myers & Bryan -- RChem

2. Accuracy -- definition
Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured.

3. What is considered accurate?
A teacher carefully measures the volume of alcohol in a 100 mL graduated cylinder with markings of 0.1 mL.
The teacher’s reading (which, of course, is correct) is mL. Several students then read the graduated cylinder.
These are their measurements: Jake: mL Lexie: mL Tyler: mL Isabelle: mL Connor: mL
Whose measurements can be considered to be accurate? Why?

4. What is considered accurate?
Metric ruler – 31 cm with 1mm (0.1cm) graduations.
To which place should the length be estimated? ____________ This estimated digit is considered to be uncertain.
How close to the accepted value do you think the measurement should be in order to be considered accurate? ______________ Why?
Accepted measurement: cm Which students are accurate?
Student measurements: Erin: cm Emily: cm Ryan: cm Manny: cm Tr’evon: cm

5. Precision -- definition
Precision refers to the closeness of a set of measurements of the same quantity measured in the same way.
(In other words, how close are a set of measurements to each other.)

6. Which data set is considered precise?
TEAM BLUE
TEAM ORANGE
42.68 g
42.56 g
43.68 g
42.58 g
42.86 g
42.57 g
39.88 g

7. When can measurements be both accurate and precise?
The measurements must be close to each other as well as the accepted value. Next page:

8. Got to #11G