Using Excel to do the Lysozyme Report

1. Be sure that your x and y axes are linear (is the distance from zero to 2 less than or the same as from 5 to 10?). To do this, use the "XY" (Excel 2003) or "scatter" (Excel 2007) choice on your menu. "Line" will not give you units that are properly spaced, and a bar graph isn't really appropriate for showing change in something with time. You can choose the X-Y scatter option that smoothly connects the points.

2. Be sure that the scale is appropriate.  There is no need for extra room on the X and Y axes. Right click on the axis, click on "format axis", then choose "scale" from the menu. You can get rid of extra stuff from there. Each graph you make should have the same Y axis scale so you can compare the graphs. A Y scale from 100 - 0% is a good choice.

3. There is a screen to produce a title and to label the X and Y axes. Do this. In Excel 2007, after selecting Insert, and Chart, go to Layout for titles and axis labels.

4. Is there more than one set of points on the graph? If so, you need a box with a legend. Excel does this by default. If you don't have more than one set of data, lose the box! The legend will say "series 1", etc. Is this meaningful? No. Change the legend so it applies to what you graphed. (e.g. "A", or "control"; something useful.) When working with a chart, a "select data" choice is available on the menu bar.

5. Got colored lines? Got a black and white printer? If you print a yellow line on a grey background, it will print as grey on grey and completely disappear. If you can't be bothered to proof your report for invisible data before passing it in, don't be surprised if I take off points. Unreadable graphs put me in a very bad mood.

6. Data transformation:  You will need to express the data from each sample as "Fraction of the initial OD".  In other words (looking at the sample  below), for 0 minutes (0.370/0.370) = 1.00; at 5 minutes, (0.364/0.370) =  ?  etc.  You will make graphs using these decimal fractions. For copying formulas in Excel, try this: instead of typing in the values, use the cell name and the modified cell name:   =B1/B$1  The $ means that you divide by whatever is in B1. You can copy this throughout the whole table and do all your calculations in two steps! Make sure you check that you got the right results! Each column of transformed data should start with 1.00.  Please, only two decimal places.