ISA Variables

ISA
The nature and type of variables in investigation skills assessments.
28 January 2011

A student obtained these results while doing an investigation to determine the possible link between the number of primary and secondary turns and the output voltage and power output of a transformer.

What type of variable is shown in this column?

Independent variable

What is the nature of the variable is shown in this column?

This is a discrete variable – (whole number of turns)

Independent variable – also discrete (whole numbers of turns.)

Independent variable, This one is continuous (can take any value).

Dependent variable – this one is continuous – can take any value.

Dependent variable – this one is a categoric variable– its value is described in words.

A student obtained these results while doing an investigation to determine the possible link between the pH (acidity) of water used on germinating cress seeds and their growth and colour.

This is a control variable – to ensure this is a fair test.

This is an independent variable – it is also a continuous variable

This is a dependent variable – it is also a continuous variable.

This is a dependent variable – it is also a category variable.

A student obtained these results while doing an investigation to determine the strength of a concrete block as the percentage cement in the mix varies.

Independent variable – This is also a continuous variable – any value of cement could be taken

Dependent variable – The value is discrete because only multiples of 10N were available

ISA Variables

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