Simple question

Use the Median function and STDEV functions to calculate data points to plot. Then plot the data points in a chart.

In your chart of multiple series, select the series of data in the chart that you want to chart differently. Change the chart typeand just the selected series will change to the new type. In this way you can chart actual expenses in a column type of chart and plot the budget data with a line type of chart on the same chart.

If you need data plotted on a secondary axis usinga different scale, right-click on the series in the chart and select Format Data Series and go to the Axis tab where you can select the Secondary Axis radio button. This will plot the selected data series on another right side axis rather than the left side value or Y-axis. Then the scale can be changed by right-clicking on the secondary axis numbers.

Office 2000 (Excel) graphs data. Use the calculational ability of Excel to create data points using the slope and y-intercept data. Then select this data and create your chart.

You can use two axis to plot the median and the std deviation on two different scales.

By having the slope and y-intercept, I assume you have a straight line. All you need to do is to plot any two points on that line.