1. Uncertainties of Measurements Precision Accuracy Parallax Error

2. All measurements are subject to uncertainties.

3. This can be due to external causes (such as environmental conditions), the way the measurements are made, or a poorly made or uncalibrated tool.

4. What is the difference between using the two different instruments? Which instrument will measure to a smaller amount?

5. Precision The degree of exactness in a measurement to which the measurement of a quantity can be reproduced.

6. Is limited by the finest division on the measuring tools scale. Precision is not affected by uncertainties of measurement. A set of measurements can be very precise but inaccurate.

7. It is important to realize that precise data--no matter how carefully measured--may be inaccurate.

8. Accuracy Closeness of a measurement to the standard value of that quantity. Describes how well the results agree with an accepted value. or refers to how close a measurement is to the true value of what is being measured.

9. Uncertainties of a measurement affect the accuracy. Is affected by how well the tool you are using is calibrated

10. Which is most accurate? Which is most precise? Which is neither? Which is both accurate and precise? B B and C A B

11. Example Three groups of students were testing the affects of applied force on the length of a spring. Each group hung a 150 g mass from the end of identical springs for four trials and measured the change in length of the spring (the actual change in length was 8.5 cm). Their results were as follows: Group 1:Group 2:Group 3: 9.6 cm 8 cm 6 cm 9.5 cm 8.5 cm 4 cm 9.75 cm 8.75 cm 7 cm 9.3 cm 8.25 cm 9 cm

12. Parallax Error (′par·ə′laks ′er·ər) The apparent shift in the position of an object when it is viewed from various angles. A parallax error in a meter reading

16. Reading a Graduated Cylinder