ISA Key Terminology

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  • Created by: Max Flynn
  • Created on: 30-05-13 14:07
An accurate measurement is one which is close to the true value
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Data refers to a collection of measurements. Data can be collected for the volume of a gas or the type of rubber.
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Data which have been subjected to some form of validation. It is possible to give a measure of importance to data which has been validated when coming to an overall judgement.
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The precision of a measurement is determined by the limits of the scale on the instrument being used. Precision is related to the smallest scale division on the measuring instrument that you are using. It may be the case that a set of precise measure
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True Value
This is the accurate value which would be found if the quantity could be measured without any errors at all.
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Variables are the things that we change, or decide not to change, in an experiment
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This involves fixing known points and then marking a scale on a measuring instrument, between these fixed points.
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There are many types of errors which can occur during experiments. Errors lead to measurements being different to what they should be: the true value.
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Random Error
These cause readings to be different from the true value. Random errors may be detected and compensated for by taking a large number of readings. Random errors may be caused by human error, a faulty technique in taking the measurements,
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Systematic Error
These cause readings to be spread about some value other than the true value; in other words, all the readings are shifted one way or the other way from the true value. A systematic error occurs when using a wrongly calibrated instrument.
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Zero Error
These are a type of systematic error. They are caused by measuring instruments that have a false zero. A zero error occurs when the needle on an ammeter fails to return to zero when no current flows, or when a top-pan balance shows a reading when the
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Independent Variables
The independent variable is the variable for which values are changed or selected by the investigator. In other words, this is the thing that you deliberately change to see what effect it has.
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Dependent Variable
The dependent variable is the variable the value of which you measure for each and every change in the independent variable.
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Control Variable
A control variable is one which may, in addition to the independent variable, affect the outcome of the investigation. This means that you should keep these variables constant; otherwise it may not be a fair test.
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Continuous Variable
A continuous variable is one which can have any numerical value. When you present the result of an investigation like this you should use a line graph.
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Categoric Variable
A categoric variable has values which are described by labels. When you present the result of an investigation like this, you should not plot the results on a line graph; you must use a bar chart or pie chart.
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Fair Test
A fair test is one in which only the independent variable has been allowed to affect the dependent variable.
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The results of an investigation may be considered reliable if the results can be repeated. If someone else can carry out your investigation and get the same results, then your results are more likely to be reliable. One way of checking reliability is
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Data is only valid for use in coming to a conclusion if the measurements taken are affected by a single independent variable only. Data is not valid if for example a fair test is not carried out or there is observer bias.
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Discrete Variable
It is a type of categoric variable whose values are restricted to whole numbers. For example, the number of carbon atoms in a chain.
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Ordered Variable
This is a type of categoric variable that can be ranked.
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Card 2




Data refers to a collection of measurements. Data can be collected for the volume of a gas or the type of rubber.

Card 3




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Card 4




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Card 5


True Value


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lisa linsdell

Key terminology that is useful to revise for any type of scientific investigation. (watch out for the missing sentence on card 18).

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