tabularray error

I am getting the error

while running the following:

Please help to resolve.

Disclaimer I would not recommend such a table layout. Please read the booktabs documentation for some good advice on how to create professional looking tables

You are missing:

You don't want tblr in math mode. Use \boldmath instead of \bm.

There are several bits to fix, look closely. I already pointed out some in a previous answer to a question of yours.

I also present a different layout that's much more readable.



The “normal table” can be improved:



Explanation: a table is not a spreadsheet. Vertical rules interrupt the flow of reading the data. Wide headers hinder readability and boldface isn't needed if the headers are clearly separated from the body.

The summation signs in the “Total” row are unnecessary and removing them makes the table more compact and so more readable.

Note also that \bar{X} is much better than \overline{X}.