Practical Skills Flashcards
(20 cards)
What is a random error?
An unpredictable fluctuation in measurements caused by uncontrollable factors, affecting precision by spreading results around the mean.
How can you reduce random errors?
Repeat measurements multiple times and calculate the average.
What is a systematic error?
A consistent error caused by faulty instruments or flawed methods, affecting accuracy by shifting all results the same way.
How do you reduce systematic errors?
Calibrate instruments, use different equipment, or improve experimental techniques.
What is a zero error?
A type of systematic error where an instrument shows a reading when the true value is zero, introducing a fixed offset.
Define precision in measurements.
How close repeated measurements are to each other; low spread means high precision.
Define accuracy in measurements.
How close a measurement is to the true or accepted value.
Can a measurement be precise but not accurate?
Yes — measurements can be consistent but all wrong due to systematic error.
What is repeatability?
The ability of the same person, using the same equipment and method, to get the same results repeatedly.
What is reproducibility?
The ability of different people, equipment, or methods to produce the same results.
What is resolution?
The smallest detectable change in a measured quantity by an instrument.
How is uncertainty different from error?
Uncertainty estimates the range within which the true value lies; errors are flaws causing deviations from the true value.
What are the three types of uncertainty?
Absolute uncertainty (fixed ± value), fractional uncertainty (ratio), and percentage uncertainty (%).
How do you estimate uncertainty in a single reading?
± half the smallest division on the instrument scale.
How do you estimate uncertainty from repeated measurements?
± half the range (largest value – smallest value).
How do you combine uncertainties when adding or subtracting measurements?
Add the absolute uncertainties.
How do you combine uncertainties when multiplying or dividing measurements?
Add the percentage (or fractional) uncertainties.
How do you combine uncertainties when raising a measurement to a power?
Multiply the percentage uncertainty by the power.
What are error bars on a graph?
Visual representations of absolute uncertainty for each data point, usually vertical for y-values.
How do you estimate the uncertainty in a graph’s gradient?
Draw the best fit line and the steepest and shallowest lines within error bars, then calculate the percentage difference.
