1. How to Measure Properly

2. The line falls between 23.1 and 23.2
Closely
The line falls between 23.1 and 23.2

3. The measurement extends between 23.1 and 23.2
23.1?

4. Therefore, we can be sure the measurement is 23.1?
This is where “estimation” comes into play…

5. Uncertainty in Measurements Person 1 2 3 4 5 Measurement (cm) 1.25
1.26
1.24
1st two numbers (1.2_) are certain.
Last number is (1.2?) uncertain.

6. Every measurement REQUIRES only 1 estimation!!!

7. Significant Figures Practice
Determine the number of significant figures in…
3.05 g

8. Significant Figures Practice
Determine the number of significant figures in…
3.05 g
3 Sig figs!

9. Significant Figures Practice
Determine the number of significant figures in…
600 g

10. Significant Figures Practice
Determine the number of significant figures in…
600 g
1 Sig fig!

11. Significant Figures Practice
Determine the number of significant figures in… s

12. Significant Figures Practice
Determine the number of significant figures in… s
4 Sig figs!

13. Significant Figures Practice
Determine the number of significant figures in… mm

14. Significant Figures Practice
Determine the number of significant figures in… mm
1 Sig fig!

15. Significant Figures Practice
Determine the number of significant figures in…
5000 kg

16. Significant Figures Practice
Determine the number of significant figures in…
5000 kg
1 Sig fig!

17. Significant Figures Practice
Determine the number of significant figures in…
3.0 x 10 m/s 8

18. Significant Figures Practice
Determine the number of significant figures in…
3.0 x 10 m/s
2 Sig figs! 8

19. Significant Figures Practice
Round each value to two significant figures.
78.9 m

20. Significant Figures Practice
Round each value to two significant figures.
78.9 m  79 m

21. Significant Figures Practice
Round each value to two significant figures. km

22. Significant Figures Practice
Round each value to two significant figures.
km  km
Or 1.4 x 10 km 5

23. I have a splitting headache…
Accuracy vs. Precision
I have a splitting headache…
Completely missed the dartboard!!!

24. Accuracy Refers how close a measurement is to the actual (true) value.
Dartboard Analogy:
The bull’s eye is the actual point where a person is aiming for.
100g

25. Accurate
“correct”. A measurement is considered accurate if correctly reflects the size of the object being measured.
How close are you to the actual/accepted value?
Does the practice of using body parts as measurement tools produce accurate results?

26. Precision
Refers how close a a group of measurements are to one another. (reproducibility)
Person 1 2 3 4 5
Measurement (cm)
1.25
1.26
1.24

27. Precise
A precise measurement is repeatable and reliable. Getting the same measurement each time.
Does the practice of using body parts as measurement tools produce precise measurements? (were all of your results the same?)

29. Accurate or precise?
Accurate and Precise!

30. Accurate or Precise?
Accurate

31. Accurate or Precise?
Accurate

32. We can never get a perfect measurement, the best that we can do is get as close as possible within the limitations of our measuring instruments.

33. Every measurement REQUIRES only 1 estimation!!!