Dr. Overy's KBase: Resources for Teaching and Learning - Glossary

• Accuracy
  A measurement result is considered accurate if it is judged to be close to the true

  value
• Calibration
  Marking a scale on a measuring instrument. This involves establishing the relationship between indications of a measuring

  instrument and standard or reference quantity values, which must be applied.

  
  For example, placing a thermometer in melting ice to see whether it reads zero, in

  order to check if it has been calibrated correctly.
• Data
  Information, either qualitative or quantitative, that has been collected
• Measurement Error
  The difference between a measured value and the true value.
• Random Error
  These cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurement to the next.  Random errors are present when any measurement is made, and cannot be corrected. The effect of random errors can be reduced by making more measurements and calculating a new mean.
• Systematic Error
  These cause readings to differ from the true value by a consistent amount each time a measurement is made.

  Sources of systematic error can include the environment, methods of observation or instruments used.

  Systematic errors cannot be dealt with by simple repeats. If a systematic error is suspected, the data collection should be repeated using a different technique or a different set of equipment, and the results compared.
• Categoric Variables
  Categoric variables have values that are labels. Eg names of insects or types of material.
• Zero Error
  Any indication that a measuring system gives a false reading when the true value of a measured quantity is zero, eg the needle on an ammeter failing to return to zero when no current flows.
  
  A zero error may result in a systematic uncertainty.
• Anomalies
  These are values in a set of results which are judged not to be part of the variation caused by random uncertainty
• Evidence
  Data which has been shown to be valid.
• Fair Test
  A fair test is one in which only the independent variable has been allowed to affect the dependent variable.
• Hypothesis
  A proposal intended to explain certain facts or observations.
• Interval
  The quantity between readings, eg a set of 6 readings equally spaced over a distance of 50 cm would give an interval of 10 centimetres.
• Precision
  Precise measurements are ones in which there is very little spread about the mean value. Precision depends only on the extent of random errors – it gives no indication of how close results are to the true value.
• Prediction
  A prediction is a statement suggesting what will happen in the future, based on observation, experience or a hypothesis
• Range
  The maximum and minimum values of the independent or dependent variables. For example a range of forces may be quoted as either: "From 0 N to 20 N" or "From 20 N to 0 N"
• Repeatable
  A measurement is repeatable if the original experimenter repeats the investigation using same method and equipment and obtains the same results
• Reproducible
  A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained.
• Resolution
  This is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading
• Sketch Graph
  A line graph that shows the general shape of the relationship between two variables. It will not have any points plotted and although the axes should be labelled they may not be scaled.
• True Value
  This is the value that would be obtained in an ideal measurement.
• Uncertainty
  The interval within which the true value can be expected to lie, with a given level of confidence or probability, eg “the speed is 20 m/s ± 1 m/s , at a level of confidence of 90 %.
• Validity
  Suitability of the investigative procedure to answer the question being asked. For example, an investigation to find out if the acceleration of an object depended upon the mass of the object would not be a valid procedure if the applied force was not controlled.
• Valid conclusion
  A conclusion supported by valid data, obtained from an appropriate experimental design and based on sound reasoning.
• Variables
  These are physical, chemical or biological quantities or characteristics.
• Continuous Variables
  Continuous variables can have values (called a quantity) that can be given a magnitude either by counting (as in the case of the number of cars) or by measurement (eg electrical current, speed etc).
• Control Variables
  A control variable is one which may, in addition to the independent variable, affect the outcome of the investigation and therefore has to be kept constant or at least monitored.
• Dependent Variable
  The dependent variable is the variable of which the value is measured for each and every change in the independent variable.
• Dependent Variable
  The dependent variable is the variable of which the value is measured for each and every change in the independent variable.
• Independent Variable
  The independent variable is the variable for which values are changed or selected by the investigator.