Adding alt text to tables, graphs, and other images or visual representations of data.
To add alt text to a table:
right click on the table.
select Table Properties.
click on the Alt Text tab.
complete the description. It should be around 123 characters (about 16 words), and should describe the table/graph/etc (for example 'Possible reasons to refer people for specialist advice, and the purpose of this advice').
You do not need to say 'An image of' or 'A table of' in alt text – the screen reader will flag this up automatically.
To make it easier for people who use screen readers to understand content if their screen reader cannot read it out. It helps add context to the surrounding text, if this refers back to an image. And it avoids confusing screen reader errors, because if there is no alt text a screen reader may just read out 'no alt text' or similar.