Autochecked checkbox with select

hello good is that I was thinking of doing this, the truth that no idea how to do it maybe you can help

By selecting a category the checkbox is activated

example:

<select> <option value="Juegos"></option> </select>

and my checkbox

<input id="privado" tabindex="7" type="checkbox" name="privado" /> 

you can activate the checkbox to select that category?

thanks :D