1. Objective
The learner will distinguish between precision & accuracy of measurements

2. Measuring means to compare something with a standard
Unit 7: Measurement
Measuring means to compare something with a standard
Measuring requires an instrument

3. Measurements Measurements Consists of two parts A Number Unit
Must have both parts
Ex: I have a cat that is 3
Measurements
months old?
days old?
years old?

4. What is Accuracy?
What does it mean to be accurate?
Accuracy tells us how CORRECT the measurement is.
Accuracy is how CLOSE a number is to what it should be.
Accuracy is determined by comparing a number to a known or accepted value.

5. What is Precision? What does it mean to be precise?
Precision is the degree to which repeated readings agree.
Precision can be the number of decimal places assigned to the measurement.
The precision of an instrument reflects the number of digits in the reading.

6. Accuracy and Precision
Accuracy and precision can not be considered independently
A number can be accurate and not precise
A number can be precise and not accurate
The use of the number determines the relative need for accuracy and precision

7. Example 1: How old are you? I am 16 years old
I am 15 years and 8 months old
I am 15years, 8 months, and 5 days old
I am 15 years, 8 months, 5 days, and 10 hours old

8. Accuracy vs. Precision for Example 1
Each of these statements is more accurate and more precise than the one before it.
Statement two is more accurate and more precise than statement one.
Statement three is more accurate and more precise than statement two.

9. Example 2: How long is a piece of string?
Johnny measures the string at 2.63 cm.
Using the same ruler, Fred measures the string at 1.98 cm.
Who is most precise?
Who is most accurate?

10. Accuracy vs. Precision for Example 2
The actual measurement is 2.65 cm.
Johnny is fairly accurate and also very precise.
Fred is very precise, however, he is not very accurate. His lack of accuracy is due to using the ruler incorrectly.

11. ACCURACY/PRECISION
You can tell the precision of a number simply by looking at it. The number of decimal places gives the precision.
Accuracy on the other hand, depends on comparing a number to a known value. Therefore, you cannot simply look at a number and tell if it is accurate.

12. Activity
Lesson 1: Linear Measurement
Unit 7: Activity 4

13. When Do We Need to Be Accurate & Precise??
Making Accurate Measurements
Accuracy (Actual) & Precision (Predict)

14. Target Examples Were we accurate or precise?
This is a random-like pattern, neither precise nor accurate. The darts are not clustered together and are not near the bull’s eye.

15. Target Examples Were we accurate or precise?
This is a precise pattern, but not accurate. The darts are clustered together but did not hit the intended mark.

16. Target Examples Were we accurate or precise?
This is an accurate pattern, but not precise.
The darts are not clustered, but their average position is the center of the bull’s eye.

17. Target Examples Were we accurate or precise?
This pattern is both precise and accurate. The darts are tightly clustered and their average position is the center of the bull's eye.

18. Ruler (Instrument of Measurement)
Demonstrate how to use a ruler
Students measure using Customary Measurements worksheet