Acurate & Precise

Accurate:
In physical science it means 'correct'. A measurement is accurate if it correctly reflects the size of the thing being measured or is near to the correctanswer. Accuracy is how close a measured value is to the actual (true) value.

Precise:
In physical science it means repeatable, reliable, getting the samemeasurement each time." In other words is how close the measured values are to each other.
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Low Accuracy
High Precision | High Accuracy
Low Precision | HighAccuracy
High Precision |

ERRORS

Systematic error:
If you measure something several times and all values are close, they may still all be wrong if there is a"Bias"
Bias is a systematic (built in) error which makes all measurements wrong by a certain amount.

Examples of Bias
* The scales read "1 kg" when there isnothing on them
* You always measure your height wearing shoes with thick soles.
* A stopwatch that takes half a second to stop when clicked

Experimental error:Occurs when you (the experimenter) make a mistake. 

Examples:
* set up your experiment incorrectly
* misread an instrument
* Make a mistake in acalculation. 

GRAPH 1
In this graph we can see that the results are accurate because they are near to 9.81 that is the real answer and they are also precisebecause the results values are close to each other. Here maybe there was a systematic error.

GRAPH 2

In this graph we can see that the results are not accuratebecause they aren’t near to the real answer and they aren’t precise because the results values are far away from each other. Here maybe there was an experimental error.