Measurement and Error Key Words

Measurements

Reliable
- The same value is obtainted each time the experiment is carried out (within acceptable limits)
Valid
- The measurements you are making will give you the data asked for or can be used to find the required data
Accuracy
- Accurately calibrated instruments have been used
- How confident you are that your results are right
Precision
- How exact is your reading, e.g. how many decimal places

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Range
- Difference between the highest and lowest value
Uncertainty
- Also known as the probable error of the measurement
- Half the range
- OR half the smallest division on the measuring equipment
- Written as +_ the uncertainty (Can't get the real symbol on the computer but the minus is under the plus)
Mean Value
- Add all the measurements together and divide by how many you have
- You might need to include the uncertainty when quoting the mean value

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Systematic
- If all the values are out by a specific amount, can be caused by a zero error on the measuring equipment
- Must be accounted for when plotting graph and taking measurements
Random
- No differences, patterns, trends or bias.
- Often fluctuate around real value so line of best fit can show the real value
Zero
- When the measuring device is supposed to be at zero it shows a different number
- As long as this is factored into the results, it shouldn't cause a problem

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