document.getElementById("#tbl-info");

<table  id = "tbl-info" class = "table table-bordered" >
        <thead>
        <tr>
            <th scope="col">Xi</th>
            <th scope="col">fi</th>
            <th scope="col">Xi.fi</th>
            <th scope="col">(Xi - x̄)²fi</th>
            <th scope="col">fri</th>
            <th scope="col">Fi</th>
            <th scope="col">Fri</th>
            <th scope="col">Opção</th>
        </tr>
        </thead>

        <tbody> </tbody>
    </table>

function insertTable(i, Xi, fi, xifi, med, fri, Fi, Fri) { //

   var html = `
        <tr>
            <td>${Xi}</td>
            <td>${fi}</td>
            <td>${xifi}</td>
            <td>${med}</td>
            <td>${fri}</td>
            <td>${Fi}</td>
            <td>${Fri}</td>
            <td>
                x
            </td>
        </tr>
   `;
      $("#tbl-info").append(html);
}