## Graphing

 Course Support Lab Contents

### Slope Calculations with an exact fit

 Figure 7
An example of the special case where all the data points line dead on a line and the uncertainties are too small to show as error bars. Determine two widely spaced locations on the best fit by selecting an x value and reading the y value with a reading uncertainty from the graph scale. Do not use data points or data values that where used to plot the graph.

 slope = $\frac{(174 \pm 1) - (118 \pm 1) c}{(110-40)s}$ = $\frac{56 \pm 2}{70}$ = $\frac{56c \pm 3.6\%}{70s}$ = $0.800c/s \pm 3.6\%$ = $0.800 \pm 0.029 c/s$

It is important to emphasize that the slope with its uncertainty is calculated from the graph and not from data used to plot the graph.