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Flashcards in Working Scientifically Deck (7)
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What are random errors

  • Random errors will shift each measurement from its true value by a random amount and in a random direction
  • These will affect reliability (because their random) but not the overall accuracy of the experiment
  • Different random errors include
  • Reaction time: any experiment where reaction time is involved
  • Parallax: the angle you view a dial (only random if you view from a random angle)
  • Measurement errors with insufficient precision: rounding up 10.25 mm on a ruler


What are systematic errors

  • Systematic errors will shift values from their true value by the same amount or fraction in the same direction each time
  • These do not affect reliability (since they're always the same) but do affect accuracy
  • Usually arise from problematic or incorrectly used equipment
  • Different types of systematic errors:
  • Scalar error: If a piece of equipment is not calibrated (e.g. a wooden ruler has shrunk), all measurements will be offset by the same amount
  • Zero error: If a piece of equipment has an offset (e.g. mass balance shows a non-zero reading when nothing is on it), all measurements will be offset by the same amount


What is validity

  • Validity relates to the experimental method and how appropriate it is in addressing the aim of the experiment
  • Several aspects relate to validity: the equipment, the experimental method and the analysis of results
  • Relates to use of independent, dependent and controlled variable


What is reliability

  • Reliability relates to how close repeated measurements are to each other
  • Can consider reliability of the experiment or reliability of a measurement
  • Reliability can affect the overall validity of the experiment


What is accuracy

  • Accuracy is how close the final result is to the correct or accepted value
  • Use of better equipment will improve accuracy as this will reduce systematic errors
  • Compare measurement value to accepted value


What is precision

  • Precision refers to the maximum resolution or the number of significant figures in a measurement
  • e.g. a clock has precision of 1 s whereas a stopwatch has precision of 0.01 s
  • Accuracy does not rely on precision