Significant Digits

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Significant Digits
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What are significant digits?

• So that we dont have endless numbers behind a
  decimal point, scientists have agreed on some
  rules to determine which numbers in a measurement
  are really important
• Significant digits are the digits of a number
  that really mean something

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Rules for significant digits

• Non-zero digits in a measurement are always
  significant.
• For example if a car odometer measures 7.2
  miles, then there are TWO significant digits
• (the 7 and the 2)

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Rules for significant digits (contd.)

• Zeros between two significant digits in a
  measurement are significant.
• For example The number 1.609 has 4
  significant digits.

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Rules for significant digits (contd.)

• All final zeros to the right of a decimal point
  are significant.
• If there is no decimal point, final zeros are NOT
  significant.
• So, 1.000 would have 4 sig. digits, but
  10 would only have 1 sig. digit.

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Rules for significant digits (contd.)

• Zeros that exist only to put the decimal point in
  the right place are NOT significant.
• So if we had 0.0008 kilometers, it would only
  have 1 sig. digit.

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How many sig. digits are there in . . .

• 36.33 minutes?
• Answer 4 significant digits

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How many significant figures are there in . . .

• 0.0074?
• Answer 2
• 0.010 kilograms?
• Answer 2

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Math for Science
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Accuracy

• How close a measurement comes to the actual or
  true value
• Correctness

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Precision

• A measure of how close a series of measurements
  are to one another
• Repeatable

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Error

• Error The difference between the accepted value
  and the value you measured in the lab

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Error Calculation

• (Accepted Experimental)
• ---------------------------------------- x
  100
• Accepted

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Types of Observations

• Quantitative number
• Qualitative like (description)
• Examples 171cm or tall
• 2.35kg or heavy 122OC or
  hot

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Scientific Notation

• (x 10) means time 10 to the __ power)
• Move Decimal Point (by of spaces)
• If positive, makes number bigger (right)
• If negative, makes number smaller (left)
• Ex 1 x 102 or 1.35 x 10-2
• Ex 385000000 or 0.000790