Readings And Measurements Flashcards
Define accuracy.
The closeness of a result to its true value.
Define precision.
The degree of closeness multiple results are to each other.
If I measure the same thing twice does it give the same result?
Define measurement error.
An error in recording a measured value.
Define a random error.
An error with no pattern or bias.
The effect of these are reduced when doing multiple tests.
Define systematic error.
Errors that show pattern or bias.
For example, faulty equipment resulting in multiple errors.
Define zero error.
An error that occurs when a measuring instrument is not zeroed.
Define reliability.
The degree of closeness to the original results if one was to repeat an experiment identically.
Define repeatable.
A measurement is repeatable if the original experimenter repeats the investigation using the same method and equipment and obtains the same results.
Define reproducible.
A measurement is reproducible if the investigation is repeated by a different person and or equipment/techniques and obtains the same results.
Define uncertainty.
The spread of values which are likely to include the accepted value. (If a value is outside this spread it is an error)
Define validity.
Is the investigative procedure suitable in answering the question being asked?
How do you find the actual uncertainty of a reading?
±half the smallest division.
Example: 1°C would be 1°C ±0.5°C
What is the actual uncertainty in a gradient (m)?
Max(m) - Min(m) / 2 = δm
So same as ±half the range.
How do you calculate the percentage uncertainty in a gradient (m)?
100 x (difference in best and worst(m) / best line(m)) = ±δ
How do you find the actual uncertainty of a measurement?
±the smallest division.
Example: 11cm would be 11cm ±1cm
How do you find the actual uncertainty of a digital reading?
± the last significant digit.
Example: 10.4cm would be 10.4cm ±0.1cm
How do you calculate percentage uncertainty?
Actual uncertainty / value of measurement x100
How do you find the actual uncertainty in a mean value?
± half the range of values.
When two measurements are multiplied how do we calculate the overall percentage uncertainty?
You sum the two separate uncertainties together.
Example: 10.2cm ±2% x 10.0cm ±4% = 102cm² ±6%
When recording data what 2 things should you do?
Record all the results in ONE table.
Note the resolution of any instruments used next to the table.
When drawing a graph what should you do?
Ensure the it has a title.
Ensure it has a sensible scale and has sensible divisions.
Do you know everything you need to about Further Uncertainty?
If no, go to book 1, page 10,
