11.1 Qualitative And Quantitative Data and 11.2 Uncertainties And Errors In Measurement And Results Flashcards
What is qualitative data?
Non numerical data obtained from an experiment lie observations made during an experiment.
What is quantitative data?
Numerical data.
What are random errors caused by?
Due to limitations of the measuring apparatus. All measurement must be quoted with an uncertainty the uncertainty indicates the size of the random error.
What uncertainty does analogue apparatus have?
Half the smallest division you take a reading to.
What uncertainty do digital instruments have?
Plus or minus the smallest division.
What are the effects of random errors?
The measurements take will be distributed either side of the mean.
How can random uncertainties be eliminated?
They can never be completely eliminated but the effect of random uncertainties can be reduced by repeating experiments more often.
When do systematic errors occur?
Due to apparatus used or the procedure of the experiment. Systematic errors are always in the same direction.
How can systematic errors be identified?
By comparison with accepted literature values for quantities. We can use percentage errors to compare the experimental value with the accepted literature value.
How is the percentage uncertainty calculated?
percentage error =
(experimental value - accepted value/ accepted value) x 100
What does it mean if the percentage error is greater than the percentage uncertainty due to random errors?
The experiment involves some systematic errors.
What does it mean if the percentage error is smaller than the percentage uncertainty?
Any deviation from the literature value can be explained in terms of random errors that is the limitations of he measuring apparatus.
How is the uncertainty usually quoted?
To 1sf - values should be stated so that the uncertainty is in the last significant figure ie. no figures quoted after the uncertainty.
What is precision?
Relates to the reproducibility of results, high precision means that repeat values are close together and close to the mean.
What is accuracy?
Accuracy refers to how close a measurement is tot he actual value of a particular quantity. Low accuracy is due to systematic errors within the experimental procedure.
When adding or subtracting numbers what happens to the decimal places?
The final answer should be quoted to the same number of decimal places as the piece of original data that has the fewest decimal places.
When multiplying or dividing numbers what happens to the significant figures?
The final answer should be quoted to the same number of significant figures as the piece of data with the fewest significant figures.
How is the percentage uncertainty calculated for a piece of data?
(absolute uncertainty / value) x 100
How is the absolute uncertainty calculated for a piece of data?
(percentage uncertainty / 100) x value
What happens when quantities with uncertainties are added or subtracted?
The absolute uncertainties are added.
What happens when quantities with uncertainties are multiplied or divided?
The percentage uncertainties are added to give the percentage uncertainty of the final value.
What happens when multiplying or dividing a quantity with a pure number?
The percentage uncertainty stays the same.
