Unit prefixes, uncertainites and errors Flashcards
What are the 7 International SI units?
• Meter
• Kilogram
• Second
• Ampere
• Mol
• Kelvin
• Candela
What is a random error?
An error that causes readings to be spread about the true value due to the results varying in an unpredictable way.
What is a systematic error?
An error that causes each reading to be different from the true value by the same amount.
Does a random error affect precision or accuracy?
Precision
Does a systematic error affect precision or accuracy?
Accuracy
Why can’t you correct random errors?
Because they are unpredictable.
What are systematic errors caused by?
• The environment
• The apparatus your using
• Your experimental method
Why is it hard to correct systematic errors?
You don’t know they are there since they all differ from the true value by the same amount.
What should you do if you suspect a systematic error?
Repeat the experiment with a different technique or apparatus and compare the results.
State and explain 3 ways to reduce uncertainties:
• Repeat the experiment and calculate a mean.
• Check your data for anomalies (if there are any, don’t include them when calculating a mean).
• Using the most appropriate apparatus e.g. a micrometer instead of a millimetre ruler.
What is the formula to calculate the percentage uncertainty?
(Absolute uncertainty/Total Value) x100
What should you do to the uncertainties when adding or subtracting data?
Add the absolute uncertainties.
What should you do to the uncertainties when multiplying or dividing data?
Add the percentage uncertainties.
What should you do to the uncertainties when raising to a power?
Multiply the percentage uncertainties by the power.
What is discrete data?
Data that can only take specific, distinct values; this involves counting with whole numbers.
What is continuous data?
Data that has a continuous variable of any value on a scale. You can never measure the exact value of a continuous variable.
What is categoric data?
Data that is organised into categories e.g. materials: wood, metal etc..
What is ordered (ordinal) data?
Data that is organised into categories put in order e.g. organising frequencies of light into “low”, “medium” and “high”.
What is precision?
How much your data spreads from the mean/true value.
What is accuracy?
How close the result is to the true value.
What is a repeatable result?
When you can repeat the experiment several times and get the same result.
What is a reproducible result?
When someone can recreate your experiment using different apparatus or methods and get the same results as you.
