Drill accuracy grade by sanmelody


Part 1- A single single unit conversion
Convert 0.1 (or 10-1) m to ___ cm. Give answer in
  scientific notation.

Part 2 - Draw 3 dart boards
• On one, show 6+ darts that have accuracy (on
  average), but no precision
• On another, show 6+ darts that have precision
  but no accuracy
• On the last, show 6+ darts that have accuracy
  and precision.
            Target analogy

but no
        Target analogy

but no accuracy
        Target analogy

& Precision!
        Extra credit assignment
         due Wednesday 9/27
• Make a cartoon poster for one safety rule.
• If it looks good enough to me, I will
  laminate it & put it up in the classroom.
• It should be:
  – No dialogue, just pictures with the safety rule
    as a caption underneath
  – Big enough to see from across the room
  – Funny is good, but it needs to be clearly
    related to the safety rule.
      Accuracy ≠ Precision!!!
• If there is accuracy  does not
  necessarily mean there is precision.

• If there is precision  does not
  necessarily mean there is accuracy.
  Making precision quantitative
• Scientists speak in numbers a lot.
•          1 = 1.000 000 000?
  – Not for scientists!
• Which number is more precise?
• So what?
     Which would you prefer?
    Copy & circle column A or B.
        A                       B

Salary = $1,000/wk    Salary = $1000.00/wk

Chemistry grade: A    Chemistry grade: 96

A few grams of        3.000 grams
  chemotherapy drug     chemotherapy drug

$2 Bag of chips       $2.50 Bag of chips
  mass = 500 g
                        mass = 500.1 g
  Making precision quantitative
• When making a measurement, the data
  should only include meaningful numbers,
  based on how precise the machine is.
• Pour exactly 101 L several times into a
  graduated cylinder and read volume:
  – 100.1L, 101.2 L, 103.9 L,102.0 L
• Which numbers change? Which stay the
• Machine is precise only to tens place.
    Significant Digits (Sig. Dig.)
• AKA Significant Figures (Sig. Fig.)
• Sig Fig = # of meaningful numbers plus 1st
  number that has uncertainty:
• GC from last slide:
  – 100.1L, 101.2 L, 103.9 L,102.0 L
• 1st number of uncertainty is in singles’ place.
• So, when measuring a volume around 100 L in
  this GC, write down 3 # or 3 Sig. Fig.
  – 100 L, 101 L, 104 L,102 L
         Class examples
• 4 meausurements:
     When you are reading other
        people’s numbers:
• All non-zero numbers are significant
• All trailing zeroes are significant ONLY IF
  there is a decimal point
• All zeroes between no-zeroes are
• Place-holder zeroes are not significant.

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