BIOL 1406

PreLab 1.2


When measuring a random variable, what units of measurement should I use?

Measurements of a random variable almost always consists of BOTH a number AND a unit. Failure to use appropriate units along with the numerical value makes your measurement incorrect. Scientists use the International System of Units (SI units). SI is the modern version of the “metric system”. This system is convenient for several reasons. For one, it is the standard used around the world, which makes it easy for scientists to compare their results with each other. For another, because SI units are related to each other by factors of 10, it is easy to convert from one unit to another by simply moving the decimal point to the left (if the units get bigger) or to the right (if the units get smaller.)

Below is a review of several important SI units and their prefixes.


International System of Units

Random Variable Unit Abbreviation
Distance meter m
Weight gram g
Volume liter L
Time second s
Amount of a substance mole mol


SI prefixes for units of measurement

Prefix abbreviation relationship to basic SI unit means multiply by: (to convert to basic SI unit)
Micro μ one-millionth 10-6 or 0.000001
Milli m one-thousandth 10-3 or 0.001
Centi c one-hundredth 10-2 or 0.01
Deci d one-tenth 10-1 or 0.1
Deca da ten times 10
Kilo k one thousand times 1000
Mega M one million times 1,000,000

 

Your Turn
What are the SI units for measuring distance? Check your answer.
What are the SI units for measuring weight? Check your answer.
What are the SI units for measuring volume? Check your answer.
 
How many millimeters are in 1 cm? Hint Check your answer.
How many centimeters are in 1 km? Hint Check your answer.
How many microliters are in 1 mL? Hint Check your answer.
How many microliters are in 1 dL?  Hint Check your answer.
1 kg = ? mg Hint Check your answer.

Close this browser window to return to Blackboard and complete the practice quiz and assessment quiz.