# Uncertainties in measurement

#1
Hi
I've been struggling with a question in the induction task booklet my school gave out for physics and was wondering if anybody could help.

Having never covered uncertainties in measurement before, I've searched for hours to try and find the answer, but no website seems to have the answer. The task is to match the word to the definition.

Words
• Random uncertainty
• Systematic error
• Zero error
• Parallax error
• Significant figures
Definitions
• Should not exceed that of the value given by the least precise piece of measuring equipment in the practical
• Can be reduced by repeating measurements
• Is often caused by not looking directly at the measurement device
• Can be reduced by calibrating equipment
• Is caused by the measuring equipment not displaying the correct value when disconnected
Thanks
0
6 years ago
#2
(Original post by Aquarian8luh)
Hi
I've been struggling with a question in the induction task booklet my school gave out for physics and was wondering if anybody could help.

Having never covered uncertainties in measurement before, I've searched for hours to try and find the answer, but no website seems to have the answer. The task is to match the word to the definition.

Words
• Random uncertainty
• Systematic error
• Zero error
• Parallax error
• Significant figures
Definitions
• Should not exceed that of the value given by the least precise piece of measuring equipment in the practical
• Can be reduced by repeating measurements
• Is often caused by not looking directly at the measurement device
• Can be reduced by calibrating equipment
• Is caused by the measuring equipment not displaying the correct value when disconnected
Thanks
Random errors are errors in your measurements beyond your control, which happen unpredictably.
Systematic errors are errors in your measurements which are made every time, and are usually caused either by flaws in the technique or equipment.
A zero error is where the equipment measures a non-zero value when it should be measuring zero (e.g. a micrometer might read a small distance even if it is completely closed)
To consider a parallax error, get a ruler and hold it vertically and put something in front of it. Now measure the height of that object a) looking slightly above it and b) looking slightly below it.
Significant figures is just simply how many significant figures you put your answer to.
0
#3
(Original post by 16Characters....)
Random errors are errors in your measurements beyond your control, which happen unpredictably.
Systematic errors are errors in your measurements which are made every time, and are usually caused either by flaws in the technique or equipment.
A zero error is where the equipment measures a non-zero value when it should be measuring zero (e.g. a micrometer might read a small distance even if it is completely closed)
To consider a parallax error, get a ruler and hold it vertically and put something in front of it. Now measure the height of that object a) looking slightly above it and b) looking slightly below it.
Significant figures is just simply how many significant figures you put your answer to.
Is it possible to match the words to the definitions in the question? That's what I've been stuck on
0
6 years ago
#4
(Original post by Aquarian8luh)
Is it possible to match the words to the definitions in the question? That's what I've been stuck on
The response above should be enough to help you match the words to the definitions, but I'll try to give some more detailed explanations.

To get you started - as systematic errors can be caused by problems or flaws in the equipment, it matches with the "can be reduced by calibrating equipment". Systematic errors are present no matter how many times you repeat the measurement as it's a problem with the equipment itself. One kind of systematic error is a zero error, which is when, for example, a scale doesn't show zero when there's nothing on it. Say if a scale showed +1 kg when there was nothing on it, that would mean that all your measurements were 1 kg higher than they should be.

Random errors affect each measurement you make but not in the same way as systematic errors. Say if you take the same measurement of a mass several times, if you have random errors each measurement will be different. But each measurement is just as likely to be a little over the correct value as a little under, so the more measurements you take, the closer the average gets to the real measurement. Therefore, taking more measurements reduces the effects of random errors.

Parallax error is to do with the way you look at an object. If you fill a beaker with water and place a ruler beside it, the water level will appear different when you look at different heights. This is why you should always take measurements at eye level to get an accurate result.

Significant figures is about how many decimal places you should write your answer to. If you're using a stopwatch that goes down to seconds, it only makes sense to record the time to the nearest second. If you do some calculations and come out with an answer (say an average) of 36.4 seconds on the calculator, you should only write down 34 seconds as the average, as you have no information about fractions of seconds - this is greater than the precision of the stopwatch.
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