Plotting data & Regression using the parallelogram method Annika Lohstroh 17 BB 03

Outline Plotting data Taking the data Choosing the graph scales Formatting the graph Parallelogram method Drawing the best fit line Drawing the parallelogram Determining the gradient and intercept Using your result Adding error bars to your graph Quoting the fit results

Taking data – table & graph Power supply TX Ltd Model 832 Multimeter Fluke 73 Series II 20 V scale Multimeter Fluke 73 Series II 1 mA scale Sample V [V] I [mA] … Uncertainty in the instrument ?

Plotting the graph Axis label & units Title Scale not ideal

Choosing the scale & labeling Plot as you go along Your graph does not have to show the coordinate (0/0)

Drawing the best fit line

Drawing the parallelogram The best fit line is in the centre of the two parallel lines above and below it 2/3 of the data points should lie within the parallelogramm

Determining the gradient Section1 Subsection Use a large triangle to determine the gradient m best

Determining the gradient Section1 Subsection Draw the diagonals in the parallelogram and determine their gradients

Determining the intercept Section1 Subsection Determine the intercept c for all 3 lines C min = mA C best = mA C max = mA

Using those results… Quoting your results: Never use more than 2 digits of precision for the uncertainty – round the values accordingly: Calculating the uncertainties, where n is the #data points:

Adding error bars… The error bars have the height of the parallelogram.

Adding error bars… In a formal report you may choose not to show the helping lines (parallelogram, grid lines…)

Questions ?