key science skills

• Accuracy


  How close a measurement is to true value of quantity being measured. Is not quantifiable; measurement values may be more accurate or less accurate.
• Precision


  How closely a set of measurement values agree with each other. Gives no indication of how close measurements are to true value.
• Repeatability

  Closeness of agreement between results of successive measurements of same quantity being measured, carried out under same conditions of measurement.
• Reproducibility


  Closeness of agreement between results of measurements of same quantity being measured, carried out under changed conditions of measurement.
• True value


  Value, or range of values, that would be found if quantity could be measured perfectly.
• Validity


  A measurement is to be valid if it measures what it is supposed to be measuring. Refers to how well results among the study participants represent true findings among similar individuals outside of a study.
• Internal validity


  Psychological investigation said to be internally valid if it investigates what it sets out and/or claims to investigate.
• External validity


  Psychological investigation said to be externally valid if results of research can be applied to similar individuals in different setting.
• Measurement error


  Difference between measured value and true value of what is being measured.
• Personal error


  Mistakes, miscalculations, observer errors when conducting research.
• Random errors


  Affect precision of measurement and are present in all measurements except for measurements involving counting. Are unpredictable variations in measurement process and result in spread of readings.
• Systematic errors


  Affect accuracy of a measurement. Cause readings to differ from true value by consistent amount or by same proportion each time measurement is made.
• Uncertainty


  Lack of exact knowledge of value of the quantity being measured.
• Outliers


  Readings that lie a long way from other results.
• Controlled variable


  Variables a researcher holds constant (controls) in investigation. Are not part of investigation itself – is neither independent nor dependent variable, nor same as a control group.
• Independent variable


  Variable for which quantities are manipulated (controlled, selected or changed) by researcher, and variable that's assumed to have a direct effect on dependent variable.
• Dependent variable


  Variable researcher measures, after selecting independent variable that is assumed to affect the dependent variable.
• Extraneous variable


  Any variable that's not independent variable but may affect results (dependent variable) of research.
• Confounding variable


  Variables that have affected results (dependent variable), apart from independent variable. May have been an extraneous variable that hasn't been controlled for, or can be type of variable that can't be controlled for.