Measurements and their errors Flashcards
What are each of these prefixes powers
What are the types of errors and what does each mean
- Systematic errors:
- arise from the use of faulty instruments used or from flaws in the experimental method
- This type of error is repeated consistently every time the instrument is used or the method is followed, which affects the accuracy of all readings obtained
- To reduce systematic errors:
Instruments should be recalibrated, or different instruments should be used
Corrections or adjustments should be made to the technique - Random errors:
- cause unpredictable fluctuations in an instrument’s readings as a result of uncontrollable factors, such as environmental conditions
- This affects the precision of the measurements taken, causing a wider spread of results about the mean value
- can be reduced by repeating the experiment + finding a mean value - Zero error:
- This is a type of systematic error which occurs when an instrument gives a reading when the true reading is zero
- This introduces a fixed error into readings which must be accounted for when the results are recorded
What is accuracy
- A measurement is considered accurate if it is close to the true value
- The accuracy can be increased by repeating measurements and finding a mean of the results
- Repeating measurements also helps to identify anomalies that can be omitted from the final results
What is precision
- Precise measurements are ones in which there is very little spread about the mean value, in other words, how close the measured values are to each other
- If a measurement is repeated several times, it can be described as precise when the values are very similar to, or the same as, each other
- The precision of a measurement is reflected in the values recorded - measurements to a greater number of decimal places are said to be more precise than those to a whole number
What does repeatable mean
A measurement is repeatable if the original experimenter repeats the investigation using the same method and equipment and obtains the same results
What does reproducible mean
A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained
What are the two types of uncertainty
How is absolute uncertainty measured
How is percentage uncertainty calculated (including the graphical method)
How to convert from J to eV
How to convert from J to kWh
What does it mean when a value is in an order of magnitude
When a number is expressed in an order of 10
What does it mean when a value is an order of magnitude, or two orders of magnitude, larger than another
How can precision and accuracy be shown on a graph
What is resolution
- Resolution is the smallest change in the quantity being measured of a measuring instrument that gives a perceptible change in the reading
- For example, the resolution of a wristwatch is 1 s, whereas the resolution of a digital stop-clock is typically 10 ms (0.01 s)
- In imaging, resolution can also be described as the ability to see two structures as two separate structures rather than as one fuzzy entity
