How to Make a Cumulative Frequency Table

1. Construct your spreadsheet to have three columns. One of these columns will be your observation interval, the second will be the number of observations you make per interval, and the third will be the cumulative frequency column.
2. Construct your table to contain as many rows as you have observation intervals (e.g., if you are going to make an observation every hour for one day, you will have 24 rows).
3. Write your observation intervals down in the first column. As in the above example, if you are making an observation each hour for one day, your 24 rows in this column will be numbered individually, 1 through 24.
4. Note the number of observations you make during each time interval in the second column. For example, if you observe 3 birds at your feeder at the 1-hour time mark, write the number '3' in that column. The next observation period, you may see only 2 birds.
5. Keep a running total of how many observations you have made during each time period in the third column. For example, if during time period one you observe 3 birds, after writing '3' down in your second column, also write '3' in the third column. At the second observation period you observe 2 birds, you will record '2' in the second column, but add this number to the number in the cumulative frequency column to give you the entire number of birds observed since your observations began (in this case, 5).
6. Continue writing observations at each observation interval, adding the total to the cumulative frequency and recording it in the third column.