1. Accuracy and Precision

2. Qualitative Measurements
Qualitative measurements give results that are descriptive and non-numerical.
Example: Colors, smells

3. Quantitative Measurements
Quantitative measurements give results that are definite, usually as numbers and units.
Example: 27mL

4. Accuracy and Precision
Measurements work best when they are accurate and precise

5. Accuracy
Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured.
To evaluate the accuracy of a measurement, it must be compared to the correct value.

6. Precision
Precision is a measure of how close a series of measurements are to one another.
The precision of a measurement depends on more than one measurement.

7. Accuracy and Precision
Reproducibility
Check by repeating measurements (Trials)
Poor precision results from poor technique
Correctness
Check by using different methods
Poor accuracy results from procedural or equipment flaws

8. Accuracy and Precision

9. Accuracy and Precision
In this picture, all of the darts land on the bulls-eye which illustrates good precision and accuracy.
In this picture, all of the darts land near each other, but away from the bulls-eye which illustrates good precision, but poor accuracy.

10. Accuracy and Precision
Here the darts are not close to each other, but are close to the bulls-eye indicating poor precision, but good accuracy.
Finally, the darts are not close to each other or near the bulls-eye indicating both poor accuracy and poor precision.

11. Accuracy and Precision
What is the following an example of:
You did an experiment to see at what degree water boiled in Celsius.
You got the following results.
T1- 65
T2- 67
T3 – 66
Accuracy or Precision????
99.98 C

12. Accuracy and Precision
A basketball player throws 100 free-throws; 95 of these balls go through the goal; 5 miss the goal entirely. Describe the precision and accuracy of the free-throws. Both

13. Accuracy and Precision
The same player is having an off day; 5 balls go through the goal; the other 95 balls bounce off of the rim. Describe the precision and accuracy of the throws. Precise, but not accurate

14. Accuracy and Precision
Each of five students used the same ruler to measure the length of the same pencil. The results are as follows: cm, cm, cm, cm, cm. The actual length of the pencil was cm. Describe whether accuracy and precision are each good or poor for these measurements.

15. Draw a target diagram that shows precision but not accuracy .

16. Draw a target diagram that shows accuracy but not precision

17. Draw a target diagram that shows both accuracy and precision

18. Practice
a)78.1 mL, 43.9 mL, 2 mL (should be 100mL) Precise, Accurate, Both, Neither b) 68.1 mL, 68.2 mL, 68.0 mL (should be 68.1mL) c) 98.0 mL, 98.2 mL, 97.9 mL (should be 100mL) d) 72.0 mL, 60.3 mL, 68.1 mL (should be 100mL)