Error radio buttons

Dear friends, I have a form with radio check boxes, on submission to Php snippet output should be score ! if user clicks right answer, otherwise score-0 However it is repeatedly giving me score-1 irrespective of correct radio button is clicked or incorrect radio button is clicked. Any guidance, please. -------------------------------------------------------------- php code ----------------------------------------------------------- <?php $variable = 3 ; if ($variable == 3) { echo "Score 1"; } else { echo "Score 0"; }; ?> ----------------------------------------------------------------- html form code ---------------------------------------------------------------- <html> <head> <title></title> </head> <body> <form method="POST" action="quiz.php"> Q-1)Law of diminished return is ;<br> <input type="radio" value="4" checked name="R"> Medical concept <BR> <input type="radio" value="3" checked name="R"> Economic <BR> <input type="radio" value="2" checked name="R"> Agriculture <BR> <input type="radio" value="1" checked name="R"> Computers <BR> <INPUT TYPE="SUBMIT" NAME="submit" VALUE="See Score"> </form></body> </html>