The table summary is excessively verbose, and practically the information it provides is too much without the context of the table's actual contents as to be useful.
Summary should not include column descriptions.
Add scope=”row” to the th cells in the top table. Remove the long summary and use summary=”Participants” instead. Add scope=”col” to the first row th’s. Make the first column th with scope=”row”.
Please remove headings <h3s> from within the table.