Physics lab quiz 1

Error bars

indicate range of possibilities for the true value

• every data point plotted on a graph is not the true value but an estimate of the true value

What is used to determine if two measurements are the same?

if their ranges of + or - 2 sigma overlap

Accuracy

a measure of how closely the results agree with a true or accepted value

• in many scientific investigations the actual true value is not known so claims of accuracy cannot be made

Precision

the repeatability of similar measurements under unchanged conditions and does not require knowledge of the true value

• the degree to which future measurements yield same results

Precision improves as…

random error decreases

Accuracy improves as…

systematic error decreases

Random error

random fluctuations in the measurements due to limitations of the measuring device or technique

Systematic error

uncertainties in measurements due to reproducible conditions in the system or biases in the observational method that can shift results in one direction

• much harder to estimate

• cannot be eliminated by averaging or by stats

In this experiment stopwatches are replaced with what and why?

motion sensor → allows for a precise time measurement and reduces random error low enough that systematic error can be seen in the data