Chapter 1: Measurement and Conversions

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Chapter 1 Measurement and Conversions
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Measurement
All measured values have a number and a
unit. Joe weighs 82. 82 what? 82 pounds? 82
kilograms? Joe weighs 82 kg. Lori is taking
400 mg of ibuprofen for her headache. Johns
height is 1.8 m.
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Accuracy and Precision
Measurements are subject to error, so they are
often repeated.
Accuracy How close a measured value is to its
true value
Precision How close multiple measurements are
to each other (reproducible)
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Accuracy and Precision
Not Accurate Not Precise

Accurate Not Precise
Not Accurate Precise
Accurate Precise


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Accuracy and Precision

• Nurse A and Nurse B both measure the length of a
  screaming, squirming newborn baby three times
• Nurse A Nurse B
• 50 cm (20 in) 1) 150.0 cm (59.1 in)
• 45 cm (18 in) 2) 150.5 cm (59.3 in)
• 55 cm (22 in) 3) 149.9 cm (59.0 in)
• Which nurse measured more accurately?
• Which nurse measured more precisely?

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Metric System of Measurement Base Units
You should know the metric base units and their
corresponding symbols.
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Prefixes Added to Base Units of Measurement and
Are Related by a Factor of 10
The same prefixes are used for all types of
metric measurements (mass, volume, etc).
You need to know these prefixes for the course
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Prefixes Added to Base Units of Measurement and
Are Related by a Factor of 10
1) Joe weighs 82 kg. How many g is this? 2)
Jane ran 5 km. How many m is this? 3) How many
mL are in a L? 4) How many mL are in 1 mL?
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Scientific Notation

• For very large or very small numbers, scientific
  notation is used.
• Expressed as y x 10n, where y 1-10
• Example 1 mole 6.02 x 1023
• 602000000000000000000000
• Write in scientific notation
• 2700
• 0.0032
• Convert to ordinary (decimal) notation
• 4.27 x 104
• 7.6 x 10-6

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Conversions Between Different Units of Measurement
Original quantity
Conversion factor
Desired quantity
X

When converting between different units of
measurement a. You are multiplying by 1
(conversion factor 1) b. Hence, the original
and calculated quantity are equal to each other
just expressed in a different unit.
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Conversions Between Different Units of Measurement
Example The average mass of a human liver is
1.5 kg. How many pounds is this? (1 kg 2.2
lb) 1.5 kg x (2.2 lb / 1 kg) 3.3 lb
Conversion factor 1
Original quantity
Desired quantity Original quantity
kg units cancel out, leaving the lb unit
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Performing Conversions

• A blood vessel is 0.40 mm in diameter.
• a. How many meters is this?
• b. Write the answer in scientific notation.
• c. How many inches is this? (1 inch 2.54 cm)
• d. Write the answer in scientific notation.
• Which is larger 6 L or 2 gallons? (1 gallon
  3.79 L)

I do not expect you to memorize conversion
factors between the English and metric
systems (e.g. 1 kg 2.2 lb, 1 in 2.54 cm)
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Further Problem Solving

• 1) A woman was told to take a dose of 1.5 g
  calcium daily. How many 500 mg tablets is this?
• If the pediatric dose of warfarin is 0.2 mg/kg,
  what dose should a 4-year old child be
  administered if he weighs 36 lb?
• A vial contains 25 mg/mL of a drug. To
  administer 15 mg of the drug, how many mL should
  be drawn from the vial?
• A patient is to receive 50 cc of a drug mixture
  intravenously over a 1 hr time period. What is
  the appropriate IV drip rate in gtt/min? (cc
  cubic centimeter, gtt drop)
• 1 cc 1 mL
• 15 gtt 15 drops 1 mL