October 28

There are new notes on Sigfigs today!
Topic for today are Accuracy and Precision.

Precision is how reproducible a measurement is compared to other similiar measurements.
Accuracy is how close the measument (or average measuremen) comes to the accepted or real value.

Measurement and Uncertainty
-no measurement is exact.
-every measurement is best estimate
-except if we can count the # of objects

Absolute Uncertainty
-Uncertainty expressed in the units of measurement (not as ratio)

-Method 1: make at least 3 measurements and calculate the average. Absolute unit is the largest difference between average and lowest/highest reasonable measurement. (ie. discard unreasonable data 1st!!)

-Method 2: determine the uncertainty of each instrument. Measure to the best precision when making a measurement= estimate to a fraction 0.1 of the smallest segment on instrumental scale.
EX. ruler has smallest division of 1mm, so best precision should be break into 10 equal pieces over 1mm.

Relative Uncertainty and Sigfigs!
1). Relative Uncertainty = absolute uncertainty / estimated measurement.
 can be expressed in percent %
EX. 0.05 cm +/- 0.01
(0.01/ 0.05) (100%) = 20% relative uncertainty.
2). or use sigfigs.

We did the Equipment Measuring Activity sheet together. With each measurement, we recorded the digits until the uncertain digit and state # of sig figs as well as Acceptable measurement which we will cover next class.


HOMEWORK:
 sig figs and accuracy and precision worksheet, Sig fig quiz on monday!