Use vertical error bars when plotting data to determine the uncertainty of the gradient and intercepts using minimum and maximum lines of best fit.

A student plots displacement versus time data with vertical error bars and draws minimum and maximum lines of best fit through the error bars. Which feature of the graph is most directly determined by the separation between these two lines at the vertical axis?

A student investigates the relationship between applied force and spring extension. The graph shows the experimental data with vertical error bars representing measurement uncertainty in extension. Determine the uncertainty in the gradient using the maximum and minimum lines of best fit.

A student plots extension against load for a spring and includes vertical error bars on each data point. The student then draws the line of best fit and two additional lines representing the minimum and maximum possible gradients. Which statement correctly describes how to use these three lines to determine the uncertainty in the gradient?