1
Life, unlike a math textbook, doesnt have all
of the answers in the back of the book. Source
lost
2
The Real World

• Technicians get paid a reasonable salary to
  follow recipes.
• Scientists get paid higher salaries to write
  recipes for technicians to follow.

3
Good Time to Review Definitions of Precision and
Accuracy

• Precision
• Random errors are small
• Give examples of random errors
• Results are extremely reproducible
• Large number of significant digits can be
  justified
• Experimenter is skilled
• Accuracy
• Systematic errors are small
• Give examples of systematic errors
• Result reveals truth

4

• Experiments with large random errors
• Social sciences
• Political polling
• Economics
• Opinion polls
• Astronomical measurements
• Cosmic Ray research!
• The value of the Hubble constant
• Experiments with large systematic errors
• Poorly calibrated equipment
• Consistent parallax
• Voltmeter with low input impedance or inaccurate
  components
• Basically indefensible

5
A Digression on Error Analysis and Significant
Digits

• The number of significant digits that you
  report in lab reports will be taken very
  seriously
• This is where the rubber hits the road
• If too small, your work will not be taken
  seriously
• You get no credit for claiming to have measured
  the speed of light to be 3x1010 cm/sec in 2009!
• If too large, your work is indefensible and
  effectively fraudulent. (You are claiming
  something you have, in fact, not done.)

6
How Do You Determine How May Digits Are Really
Justified?

• Hg manometer?
• What are the sources of systematic error?
• How could you calibrate your measurements?
• How precisely (or is it accurately?) can you read
  the mercury levels?
• Other gauges
• How do you calibrate them?
• How precisely (or is it accurately?) can you read
  them?