Variables

When scientists undertake an investigation they will look to find a relationship between two variables.There are different types of variables

and these can be described or measured in different ways.

10 April 2023

Types of variables

• Independent variable: This is the variable that you change during the experiment. You set the value for each reading.

• Dependent variable: This is the variable that is measured during the experiment in order to find out how the independent variable affects it.

• Control variables: These are the variables that are kept constant during the experiment in order the make the test fair.

Example In this experiment the

ability of different metals to conduct heat is investigated.

The time it takes for the heat to flow through the metal and melt the wax holding the match is measured.

Independent variable = type of metalDependent variable = time it takes for the match to fallControl variables = length and thickness of the metal rods.

Description of variables

• Continuous variable: This type of variable can take any numerical value. We usually use line graphs with these.

• Discrete variable: his type of variable has certain fixed values only – usually whole numbers.

• Categoric variable: This type of variable is described by words. They have no numerical value. We usually use bar charts with these.

Examples In this experiment the

ability of different metals to conduct heat is investigated.

The time it takes for the heat to flow through the metal and melt the wax holding the match is measured.

Type of metal = categoric variableTime it takes for the match to fall = continuous variableThere are no discrete variables in this experiment

Errors

• Systematic error: this is an error in the way in which the investigation is being done – the error will always occur until the method is changed.

• Random error – this is a one off error – usually due to an incorrect reading of an instrument.

• Zero error – this is an error on the instrument being used – all the readings will be incorrect because the instrument is not calibrated correctly.

More important terms

• Anomalous results: This is an odd result that does not fit the pattern of the other results.

• Reliable results: Results which are reliable are likely to give the same result if repeated.

• Precise results: These are results that are given to a high number of decimal places.

• Accurate results: These are results which are close to the real correct result for the investigation.