Precision, Accuracy, Errors And Uncertainty Flashcards
What is always present in measurements, indicating that no measurement is perfect?
Uncertainty
This uncertainty arises from factors like imperfect equipment and measurement techniques.
What defines uncertainty in a reading?
An estimate of the difference between the reading and the true value of the quantity being measured.
What characterizes a precise reading?
Very little spread about a mean value
Example: Pendulum oscillation period (T) measurements showing values close to each other.
What is the definition of precision in measurements?
The closeness of a set of measurements to each other.
True or False: Precision is the same as accuracy.
False
Precision refers to the repeatability of measurements, while accuracy refers to how close a measurement is to the true value.
What does accuracy in measurements refer to?
If the measured value is closer to the true value.
What factors does uncertainty depend on?
- Precision of calibration of instrument
- Ability to observe
- Imperfect equipment
- Poor measuring technique
What is the relationship between observations and theory in physics?
Physics observations lead to a theory that can be tested by practical experiments.
What is essential for conducting practical exercises in physics?
The ability to carry out practical exercises in a logical and scientific way.
What should be ensured when using experimental techniques?
Be sure of experimental techniques, using apparatus and following instructions.
What is the smallest division you have to identify for single measurements?
The smallest division is used as an uncertainty.
What rule is used for multiple measurements?
The HALF RANGE RULE.
To what precision do vernier calipers measure?
Vernier calipers measure to 0.02 mm.
What should be done when measuring with a vernier caliper?
Measure multiple times from different places and calculate an average.
To what precision does a vernier micrometer measure?
A vernier micrometer measures to the nearest 0.01 mm.
What should you check for before starting to measure?
Check for zero error.
What should you do if there is a positive zero error?
Subtract from the final reading.
What should you do if there is a negative zero error?
Add to the final reading.
What are zero errors known as?
Systematic errors.
What causes systematic errors?
Systematic errors are due to the type of measuring tool.
How can zero errors be accounted for in final measurements?
We can take these into account when giving the final answer.
What is a systemic error?
Readings differ from the true value by the same amount each time
Example: Magnets getting weaker, same eye view causing parallax.
What is a zero error?
A fixed error due to equipment
This type of error can affect measurements directly.
What is a random error?
An error that may be above or below the true value
Random errors cannot be corrected but can be minimized by taking several readings.
What is the difference between an error and an uncertainty?
Error is a problem causing the measurement to differ from the true value; uncertainty is an actual range of values around a measurement
It is important to note that ‘human error’ should never be used to define error.
How is uncertainty defined?
An actual range of values around a measurement within which the true value is expected to lie
Uncertainty is expressed as a number with a unit.
If the true value is not known, what are two ways to estimate uncertainty?
- Smallest division of a measuring tool
- Use the range rule (max - min)
This helps to estimate the difference between the true value and actual reading.
What is the formula for calculating absolute uncertainty?
Absolute uncertainty is calculated as the mean of the range divided by 2
Example: If the readings are 22.7 cm and 22.9 cm, absolute uncertainty would be (22.9 - 22.7) / 2 = 0.1 cm.
Fill in the blank: A _______ error can be corrected.
Systemic
True or False: Random errors can be completely eliminated.
False
What does ‘A’ represent in the context of uncertainty?
The estimate of the difference between the true value and actual reading
‘A’ is written to significant figures.
What is the absolute uncertainty if the maximum reading is 23.1 cm and the minimum reading is 22.7 cm?
0.2 cm
Absolute uncertainty is calculated as (max - min) / 2.
How do you calculate the half range rule?
(max-min) / 2
How do you calculate percentage uncertainty?
Absolute uncertainty / measured value x100
