Module 2 Foundations

• uncertainty

  the interval within the true value can be expected to lie
• uncertainty in single measurements

  is equal to the resolution of the measuring device
• uncertainty in an average

  half the range of repeat readings
• precision


  how close repeated measurements are to each other
• accuracy


  how close a measurement is the true value
• tera


  10^12
• giga


  10^9
• mega


  10^6
• kilo


  10^3
• centi


  10^-2
• milli


  10^-3
• micro


  10^-6
• nano


  10^-9
• peta


  10^15
• pico


  10^-12
• femta


  10^-15
• homogeneous


  if both sides of the equation are equal
• random error


  measurements can vary unpredictably, caused by factors not controlled in the experiment, difficulty in deciding on the reading given by a measuring device
• systematic error


  measurement errors which the measurements differ from the values by a consistent amount each time, caused by the way the measurements are taken, faulty measuring devices
• zero error


  when the reading is not zero but the true value of the quantity being measured in zero
• percentage uncertainty


  (uncertainty in value/value) x 100
• adding or subtracting uncertainties


  add the absolute uncertainties
• multiplying or dividing uncertainties

  add percentage uncertainties
• uncertainty is raised to a power

  multiply percentage uncertainty by the power
• error bars


  show the uncertainty on a plotted graph
• line of best fit (uncertainties)


  should go through every error bar
• absolute uncertainty in the gradient

  difference between the best and worst gradient
• absolute uncertainty y-intercept 


  difference between the best and worst y-intercept