accuracyprecisionerrordfgjgkhghv_notes.ppt

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1. Chapter 3: Measurement:
Accuracy, Precision, and Error

2. Objectives
•Distinguishamong accuracy, precision,
and error of a measurement

3. Measurements
•Measurement
–quantity that has both a number and a unit
–fundamental to experimental science so must
be able take and evaluate them

4. Evaluating measurements
•Accuracy
–measure of how close a measurement comes to
the actual or true value of whatever is
measured.
•Precision
–measure of how close a series of
measurements are to one another.

5. Evaluating measurements
•Accuracy vs. Precision

6. Evaluating measurements

7. Evaluating measurements
•Often, we are experimentally determining a
value in the lab that is already known.
–When we do this, we must calculate error in
order to see how accurate and precise our
results are
•In lab reports, you will be required to
determine your error and percent error.

8. Evaluating measurements
•To determine Error:
–The accepted valueis the correct value based
on reliable references.
–The experimental valueis the value measured
in the lab.
–The difference between the experimental value
and the accepted value is called the error.
–.

9. Evaluating measurements
•To determine Percent Error:
–The percent erroris the absolute value of the
error divided by the accepted value, multiplied
by 100%.
–.

10. Practice: error and percent error
Question 1
•The accepted value for the boiling point of
water is 100.0°C. In the lab, you
experimentally determined it to be 98.7°C.
What is the error and percent error?

11. Practice: error and percent error
Answer 1
•Given
–Accepted value = 100.0°C
–Experimental value = 98.7°C
•Work
–.
–Error = 98.7°C -100.0°C = -1.3°C
–.