JSFiddle - React, Tailwind, and code Playground

HTML

<select class="form-dropdown" id="drop1" name="drop1">
    <option value=""></option>
    <option value="In Process">In Process</option>
    <option value="KIV">KIV</option>
    <option value="Completed">Completed</option>
</select>
<input type="checkbox" id="checkbox1" name="checkbox1" />

JavaScript

function sdp4(str) {
    if (str == '' || str == "In Process" || str == "KIV") {
        $('#checkbox1').prop('checked', false);
    } else {
        $('#checkbox1').prop('checked', true);
    }
}
$(function () {
    $('select').change(function () {
        var str = $(this).val();
        sdp4(str);
    });
});