Keywords

• Independent Variable - The variable you choose to change an investigation.
• Dependent Variable - The variable which you measure every time you change the value of the independent variable.
• Controlled Variable - A variable which may affect the results of the investigation and therefore should be kept constant.
• Range - The highest and lowest values of the independent variable. These should not be too big or too small.
• Valid Conclusion - A conclusion supported by the results of data from a well-designed investigation and based on good specific knowledge.
• Validity of Experimental Design - How good the method is to answer the question being asked. The method should include fair testing and controlled variables.
• Resolution - This is the smallest change in quantity being measured by a measuring instrument that can be observed. For example, plus-minus 1mm on a metre ruler.
• Anomaly - A value for set results which is seen to be much bigger or smaller than rest of the values in the set.
• True Value - The value that would be obtained in ideal conditions.
• Measurement Error - The difference between a measured value and the true value.
• Systematic Error - A systematic error is normally caused by the apparatus used and causes readings to differ from the true value by the same amount each time. The effect of systematic errors cannot by reduced by increased repeats.
• Random Error - This occurs when results vary unpredictably from one measurement to the next. These are normally due to errors by the person taking the measurements. The effect of random errors can be reduced by increased repeats and calculating a mean.
• Accuracy - A measurement result is considered accurate if it is judged to be close to the true value.
• Precision - A set of precise measurements show very little spread about the mean value.
• Repeatability - The precision obtained when repeat readings are obtained by a single person/group.
• Repeatable - If a single learner/group using the same method and equipment obtains the same or similar when they carry out the investigation again.
• Reproducibility - The precision obtained when repeat readings are obtained by different people/groups.
• Reproducible - If different learners/groups obtain the same or similar results. This should include using different equipment/methods.
• Hazard - A chemical or piece of apparatus that could cause harm. It is expected that in risk assessments the nature of the hazard is also specified. For example "Hydrogen peroxide is an irritant".
• Risk - A step in the method involving a hazard that might result in danger. For example "Hydrogen peroxide could get onto the skin when pouring it into the measuring cylinder or beaker".
• Control Measures - Something that can be done to reduce or prevent a risk while still allowing you to carry out the experiment. For example "Wash hands immediately if any hydrogen peroxide gets onto them".