Enter Data for Cases in Rows
Enter the cases into the spreadsheet, listing the data for each case in a
separate row. One column should be designated for the date of onset of
disease for each case. In the example spreadsheet below, I deleted the
names of the cases from column A, but I listed the date of onset in column
B (so this simple example just has one column for date of onset).
Sort by Date
Next sort the data set according to date of onset of disease. You can do
this by "selecting" the block of data (columns and rows) that
you want to sort using your mouse (click the left mouse button on the
upper left hand cell of the block you want to sort and hold the mouse
button down as you move the mouse down and to the right all the way to the
lower right hand cell of the block you want). Then release the mouse
button. This should highlight the block of data to be sorted. Then, from the menu at the top of the page click on "Data" and then select the "Sort" option.
This makes a dialogue box appear. Make sure that the selection "Header row" is selected at the bottom of the box if the columns have header titles. Then at the top of the dialogue box click on the selection arrow for "sort by" and chose "Date of onset". Then click on "Ok". The block of data should now be sorted by date.
Tally the Number of New Cases Each Day
Once the list is sorted by date, it easy to count up how many people became ill on a given date
(step 2 in the spreadsheet illustration).
Sometimes it is more convenient to tally the number of new cases that occurred at intervals other than 1 day. For example, the illustration below tallies new cases that occurred at 4 day intervals after 4/28, when the outbreak began.
Create a Column Graph in ExcelYou can now use the tally highlighted in blue to create a column graph illustrating the epidemic curve.
First, select the block of data with the dates and tallies (highlighted in blue). With this two-column block selected, click on the Excel graphic tool from the top menu (the icon on the top tool bar that has a little yellow, red and blue bar chart).
Then select a "column" graph of the first subtype, and click on the "finish" button. The graph will be constructed automatically. You then click on the figure legend in the graph and hit "delete" on your keyboard to spread the graph out a little.
This epidemic curve suggests a "point source" epidemic in which all the cases are exposed to a single source over a fairly brief period. The curve rises and falls fairly quickly. You can see the Excel worksheet used to construct this example in the Excel file "LaMorte - Stat Tools.XLS"