IGCSE Edexcel - General Scientific Terminology

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matthewwtts  on November 20, 2011

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IGCSE Edexcel - General Scientific Terminology

 Tanglin Trust School
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Tanglin Trust School
Accuracy An accurate measurement is one which is close to the true value. Accurate results have a mean (average) close to the true value.
Precision
This is determined by the limits of the scale on the instrument which is being used to take the measurement. The smaller the scale of division the more precise the measurement e.g. millimetres are more precise than centimetres.
Reliability Repeating an experiment or comparing data with another set of data collected the same way gives you more reliable results.
Validity Data is only valid if only one variable is changed (the independent variable). There has to be a fair test and no bias.
Fair Test Only the independent variable has been changed. All the other variables have been controlled.
Control Experiment This is an experiment which allows us to check if the chosen independent variable is the factor that causes a change in results. It allows us to make comparisons.
Dependent Variable This is the variable you measure/record. It will change as a result of changing the independent variable.
Independent Variable The values for this variable are changed or selected by the investigator. You want to see what effect it has.
Controlled Variables These variables are ones which might have an effect on the investigation and must therefore be kept the same in order to make it a fair test.
Discrete These are values that have categories or labels. The results will be presented using a bar graph. e.g. hair colour
Continuous These are values that can have any numerical value. The results should be presented using a line graph. e.g. height
Data This refers to the collection of measurements.
Hypothesis A hypothesis is a concise statement indicating what outcome they expect in an investigation. e.g. As the temperature increases the rate of enzyme activity also increases.
Compare The similarities and/or differences in sets of data need to be described.
Describe The important trends in data or points in a topic need to be stated.
Evaluate All the evidence gathered and the method of gathering data needs to looked at critically. Limitations and suggestions for improvements should be made.
Conclude Graphs, experimental data and articles should be looked at to find patterns and draw conclusions.
Explain A reason behind a theory or idea must be given using scientific knowledge and concepts.
Random Error This causes a reading to be different from the true value. Errors can be detected and compensated for by taking a large number of repeats. They can be caused by faulty equipment, human error or faulty technique.
Systematic Error All the readings taken are shifted one way or other from the true value. This could occur if a measuring instrument is wrongly calibrated.
Zero Error This is a type of systematic error. They are caused by measuring instruments that have a false zero i.e. all the measurements will be higher or lower than the true value by the same amount. e.g. a top pan balance shows a reading when there is nothing placed on the pan.
Calibration This involves fixing known points and then marking a scale on a measuring instrument between these fixed points.

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