1. Place value and rounding numbers
hundredths
thousandths
Ten-thousandths
thousands
hundreds
tens
ones
tenths

2. 56413
Round the number to the nearest hundred.

3. 56413
Round the number to the nearest hundred.
56400

4. 56.53
Round the number to the nearest whole number.

5. 56.53
Round the number to the nearest whole number. 57

6. 46.352
Round the number to the nearest hundredth.

7. 46.352
Round the number to the nearest hundredth.
46.35

8. Accuracy
Measurement of how close a measurement comes to the actual or true value
Think of accuracy like hitting the bullseye on a target.

9. Precision Can you reproduce the data Need more than one measurement
Think of this like hitting the same area of a target more than once.

10. Can you hit the bull's-eye?
Three targets with three arrows each to shoot.
Both accurate and precise
Precise but not accurate
Neither accurate nor precise
How do they compare?
Can you define accuracy vs. precision?

11. Accuracy and Precision
Accurate and Precise x x x

12. Accuracy and Precision
Precise, but they are not accurate x x x

13. Accuracy and Precision
Accurate but not Precise x x x

14. Accuracy and Precision
Not Accurate and Not Precise x x x

15. Precision of Lab Equipment
Precision refers to the reproducibility of data
The more precise a piece of equipment, the more likely you are to get the same measurement repeatedly.

16. Precision of Lab Equipment
When you look at a piece of equipment, first look at its graduations (markings) and try to find out what the lines mean.
The more precise piece of equipment has the smallest increment change between the markings
Usually the piece of equipment with the more graduations (lines) is the more precise.

17. Precision of Lab Equipment30 22 21
21.0
20.20 20 20
20.0
20.00
Increment = 1 mL
Increment = 0.2 mL
More Precise

18. a) or
More graduations – your measurements will be more precise

19. b) or
More graduations – your measurements will be more precise

20. c) or
More graduations – your measurements will be more precise

21. d) or
More graduations – your measurements will be more precise

22. Measuring Precisely: markings = 1 mL precision = 0.1 mL
RULE: All markings shown + 1 estimated digit is the precision of the equipment.
You should always estimate the last digit and always write it. Never leave it off, even if it is zero.
The number of digits including the estimated one are your “significant digits” that we will talk about next class.
markings = 1 mL precision = 0.1 mL

23. 36.4 mL Measuring Precisely: markings = 1 mL precision = 0.1 mL
RULE: All markings shown + 1 estimated digit is the precision of the equipment.
You should always estimate the last digit and always write it. Never leave it off, even if it is zero.
The number of digits including the estimated one are your “significant digits” that we will talk about next class.
markings = 1 mL precision = 0.1 mL

24. Measuring Precisely:
Markings = 0.1 cm Precision = 0.01 cm

25. Measuring Precisely:
11.65 cm
Markings = 0.1 cm Precision = 0.01 cm