You can use Attribute Equals Selector [name="value"] to get the checkboxes with particular value. Also use prop() instead of attr() as that is recommended way by jQuery doc.
Live Demo
$(":checkbox[value=4]").prop("checked","true");
or
$("input[type=checkbox][value=5]").prop("checked",true);
Description: Selects elements that have the specified attribute with a value exactly equal to a certain value, jQuery doc.
You can also do it Using attr() but prop is more appropriate for boolean properties.
$(":checkbox[value=4]").attr("checked","true");
As of jQuery 1.6, the .attr() method returns undefined for attributes
that have not been set. To retrieve and change DOM properties such as
the checked, selected, or disabled state of form elements, use the
.prop() method, jQuery doc
Edit, asked in comments, "How would look like the answer/find-expression with complex values, like value="Smith, David"
You can enclose that kind of values like Smith, David on single quotes. You can even use character used by jQuery like #, ., $ etc, see updated fiddle here.
$("input[type=checkbox][value='#Smith, David$']").attr("checked","true");
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…