The applet needs you to supply information for a weighted voting system and then press the Compute button to see the vote power distribution accoriding to the Shapley-Shubik power index.
There are several prebuilt voting systems available through the dropdown box at the bottom of the applet that appears under the Shapley-Shubik Index tab.
These can be modified and new ones can be created by making the Custom selection. At first, the table comes up with a single row. More rows can be added. If at the time when the Add Row button is pressed not row is selected, the additional row is appended at the end of the table; otherwise it is inserted after the selected row. Similarly, pressing the Remove Row button deletes either the selected row, if there is such, or the last row of the table.
The only essential information to be supplied is the weight of the newly defined player. This must be a positive integer. The name of the player does not affect the index calculations and may be left unspecified.
To define or modify a weight, select the corresponding cell either with the arrow keys or the mouse and then do one of the follwing:
Finally, do not forget to type in the Quota - also at the bottom of the applet.
Every manual change in a cell or the Quota box has to be finalized by either pressing the Enter or the Esc key or one of the navigational arrows.
Here is the applet.