1. Modified parallelogramm method Annika Lohstroh 17 BB 03 A.Lohstroh@surrey.ac.uk

2. Outline Parallelogram method - revision Drawing the best fit line Drawing the parallelogram Modified parallelogram method What if the data is “too good” ? The modified parallelogram method Calculating and using the “final” results

3. Drawing the best fit line

4. 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

5. Determining the diagonals Draw the diagonals in the parallelogram and determine their gradients

6. What if your data is not “bad enough” ? Fig. 2: Current vs Voltage

7. What if your data is not “bad enough” ? Look at the difference between fit line and measured data Fig. 3: Current vs Voltage, detail of the data shown in Fig. 2

8. Modified parallelogram method V [V] I meas [mA]I meas -I best 00.0100.010 10.343-0.0017 20.6970.0067 31.020-0.0150 41.373-0.0067 51.697-0.0283 62.050-0.0200 72.413... 82.747… 93.100…..…

9. Modified parallelogram method Fig. 4: Modified Current vs Voltage

10. Modified parallelogram method Fig. 4: Modified Current vs Voltage

11. Using those results… Using the modified fit result to correct the initial best fit line: Calculating the uncertainties, where n is the #data points: Make sure these values haven’t been rounded in a way that compromises the accuracy

12. Questions ?