How can I format a column of numbers in an emacs org mode table?

Here are the steps:

1. This is an optional one, to make things a bit more visual.C-c } turns on the overlays for row and column numbers.Same combination turns the off. Note that these are not the changesin your buffer, they're just tooltips.You might want to do C-c - on the first line, to seethe column numbers.
2. Move cursor to OUTPUT column and insert a new column with C-S-right.
3. Your cursor should now be in the new column.Type in $4=$3;%0.3f, i.e. copy the third column to the fourth,and format it as a floating point with 3 precision.Press return, and just one cell will fill in.Press C-u C-c * to recalculate all cells.This can also be done with C-c C-c, with cursoron #+TBLFM: line.
4. You can remove the old column with C-M-left if you want,and delete the table formula below.

UPDATE:

Thanks to input from @phils, here's the alternative way:

1. Move your cursor to any number in column 3, e.g. 433.275.
2. Press C-c =, cursor moves to minibuffer.
3. Enter $0;%0.3f and press return.Here $0 refers to the current column, $3 would also work if it were column 3.
4. Either press C-u C-c * anywhere in the document,or move the cursor to #+TBLFM: line and press C-c C-c.
5. Repeat the same process for column 4.