Topic 11 - Measurement & Data Processing Flashcards
uncertainty in analog scales
half of the smallest division visible on the scale
e.g. when measuring the volume on water on a measuring cylinder divided with a scale of 4ml, use ± 2ml
uncertainty in digital scales
the smallest scale division on the scale
e.g. when measuring weight and the reading says 10.00g, use 10.00 ± 0.01g
sources of uncertainty
- instrument readings
- uncertainties in judging (especially with qualitative data)
- errors
significant figures
- all the figures involved in the reading
e. g. 10.00 has 4 significant figures as the .00 denotes the level of uncertainty
types of errors
- random
- systematic
causes of random errors
- readability of measuring instrument
- effects of changes in surrounding (e.g. temperature variations)
- insufficient data
- misinterpreted readings
how to reduce the probability of random errors
repeated trials
repeatable results
if the experimenter can duplicate the experiment and observes the same results
reproducible results
if different experimenters can duplicate the experiment and observe the same results
causes of systematic errors
poor experimental design/procedure
e. g. measuring the volume of water from the top of the meniscus instead of the bottom
e. g. using an acid–base indicator whose end point does not correspond to the equivalence point of the titration
how to reduce the probability of systematic errors
careful experimental design
accuracy
smaller systematic error = higher accuracy
- small systematic errors
- gives result close to accepted value
precision
smaller random uncertainties = greater precision
- small random errors
- reproducible
graph setup (variables)
x-axis: independent variable
y-axis: dependent variable
drawing a line of best fit
- should pass as close as possible to many data points
- doesn’t have to pass through all
- can be used for extrapolation
applications of extrapolation of line of best fit
- absolute zero value can be found
- by extrapolating the vol/temp graph for an ideal gas