DEMO TOKEN SWAP TEST
DRAFT COPY ONLY.
© 2003-2006, G. William Moore, MD, PhD.
All Rights Reserved.
http://www.netautopsy.org/toknswap.htm

To perform a TOKEN SWAP TEST, enter the cell totals in the four cell-boxes of the contingency table. Then click on the SUBMIT button:

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WHAT IS THE TOKEN SWAP TEST?

      A 2 × 2 CONTINGENCY TABLE is a rectangular table, consisting of two rows and two columns. In a typical medical informatics application, the rows represent Y/N for an existing standard ("gold standard"), and columns represent a new test for a similar process.

      The TOKEN SWAP TEST (TST) is a statistical-type significance test, that is suitable for use on 2 x 2 contingency tables containing data on retrospective medical databases. The TST does not depend upon the usual statistical assumptions about repeated, random sampling from a source population, as required by other contingency table tests, such as the CHISQUARE TEST (CST) and the FISHER EXACT TEST (FXT).

Token Swap Test: References.

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Token Swap Test: Perl Source Code.

### (C) COPYRIGHT G. WILLIAM MOORE, MD, PhD, BALTIMORE, MD, 2003.
### toknswap.cgi: PERL script to perform the TOKEN SWAP TEST.
### Last modified: 8/31/2003, G. William Moore, MD, PhD.
### 
### CONSTANTS.
 $amp=chr(38);
### 
### PRINT HEADER.
 print qq| <html><head><title> DEMO TOKEN SWAP TEST. </title></head><body> |;
 print qq|\n<!-- Last modified: 8/31/2003, G. William Moore, MD, PhD.-->|;
 print qq|\n <h2><center> MODAL LOGIC INFERENCE THEORY. |;
 print qq|\n <br> DEMO TOKEN SWAP TEST <br> DRAFT COPY ONLY. |;
 print qq|\n <br><a href="http://www.netautopsy.org/toknswap.htm"> |;
 print qq|\n http://www.netautopsy.org/toknswap.htm </a> |;
 print qq|\n <br> © 2003, G. William Moore, MD, PhD,|;
 print qq|\n <br> Baltimore, MD, 2003. |;
 print qq|\n <br> All Rights Reserved. </center></h2> |;
### 
### CAPTURE INPUT DATA FROM ENVIRONMENTAL VARIABLES.
 $inpdt=lc($ENV{'QUERY_STRING'}); chop; $srqln=$amp.$inpdt.$amp;
### 
### SPLIT THE INPUT QUERY BY AMPERSAND TO OBTAIN ARRAY @qin.
 ($scr,$clahi)=split(/cla=/,$srqln,2); ($clax,$scr)=split(/\&/,$clahi,2); 
 ($scr,$clbhi)=split(/clb=/,$srqln,2); ($clbx,$scr)=split(/\&/,$clbhi,2); 
 ($scr,$clchi)=split(/clc=/,$srqln,2); ($clcx,$scr)=split(/\&/,$clchi,2); 
 ($scr,$cldhi)=split(/cld=/,$srqln,2); ($cldx,$scr)=split(/\&/,$cldhi,2); 
 $obs[1]=$clax-0; $obs[2]=$clbx-0; $obs[3]=$clcx-0; $obs[4]=$cldx-0;
 $oba=$clax-0; $obb=$clbx-0; $obc=$clcx-0; $obd=$cldx-0;
### 
### CALCULATE MARGINAL TOTALS.
 $mgn[1]=$obs[1]+$obs[2]; $mgn[2]=$obs[3]+$obs[4];
 $mgn[3]=$obs[1]+$obs[3]; $mgn[4]=$obs[2]+$obs[4];
 $gtot=$obs[1]+$obs[2]+$obs[3]+$obs[4];
### 
### ZERO THE PROBABILITY DISTRIBUTION.
 $iii=-1; while($iii<1005){$iii++; $pdsn[$iii]=0;};
### 
### PRINT MARGINAL TOTALS.
 $ao=$obs[1]; $vx=$mgn[1]; $wx=$mgn[2]; $xx=$mgn[3]; $yx=$mgn[4]; $zx=$gtot;
### 
### ERROR IF GRAND TOTAL, $gtot, IS GREATER THAN 1000.
 if($gtot>1000){print qq|\n<br> ERROR: The grand total, $gtot, is too large.|;
   print qq|\n It must be at most 500. <br> Job Terminated. |;
   print qq|\n <hr> Last modified: 8/31/2003, G. William Moore, MD, PhD. |;
   print qq| <br></body></html><br><br> \n\n\n\n |; exit;};
### 
### ERROR IF MORE THAN ONE ZERO CELL VALUE.
 $iii=0; $clv=0; while($iii<4){$iii++; $vli=$obs[$iii];if($vli<1){$clv++;};};
 if($clv>1){print qq|\n<br> ERROR: At least three cell totals must be |;
   print qq|\n greater than zero. <br> Job Terminated. |;
   print qq|\n <hr> Last modified: 8/31/2003, G. William Moore, MD, PhD. |;
   print qq| <br></body></html><br><br> \n\n\n\n |; exit;};
### 
### CALCULATE EXPECTED VALUES.
 $exv[1]=($mgn[1]*$mgn[3])/$gtot; $exv[2]=($mgn[1]*$mgn[4])/$gtot;
 $exv[3]=($mgn[2]*$mgn[3])/$gtot; $exv[4]=($mgn[2]*$mgn[4])/$gtot;
### 
### CALCULATE EXPECTED VALUES.
 $exd[1]=int((10*$exv[1]))/10; $exd[2]=int((10*$exv[2]))/10;
 $exd[3]=int((10*$exv[3]))/10; $exd[4]=int((10*$exv[4]))/10;
 $ax=int($exv[1]); $bx=$vx-$ax; $cx=$xx-$ax; $dx=$yx-$bx;
### 
### UNARY PROBABILITY DISTRIBUTION.
 $pdsn[$ax]=1; $itera=0; while($itera<$gtot){$itera++;
 $iii=0; while($iii<$gtot){$iii++; $ai=$iii; $bi=$vx-$ai; $ci=$xx-$ai;
 $di=$yx-$bi; $ah=$iii-1; $bh=$vx-$ah; $ch=$xx-$ah; $dh=$yx-$bh;
 $qh=($bh*$ch)/(($bh*$ch)+($ah*$dh)); $aj=$iii+1; $bj=$vx-$aj;
 $cj=$xx-$aj; $dj=$yx-$bj; $qj=($aj*$dj)/(($bj*$cj)+($aj*$dj));
 $pdsx[$iii]=($qh*$pdsn[$ah])+($qj*$pdsn[$aj]);};
 $iii=0; while($iii<$gtot){$iii++;$pdsn[$iii]=$pdsx[$iii];};
 if($pdsn[$ao]>0){$itera=$gtot;};}; $tknsw=$pdsn[$ao];
 $itknswd=int($tknsw*10000000);
 $tknswd=$itknswd/10000000;
 if($itknswd<1){$tknswd="<0.00000001";};
### 
### CALCULATE CHISQUARE TERMS.
 $chv[1]=(($obs[1]-$exv[1])*($obs[1]-$exv[1]))/$exv[1];
 $chv[2]=(($obs[2]-$exv[2])*($obs[2]-$exv[2]))/$exv[2];
 $chv[3]=(($obs[3]-$exv[3])*($obs[3]-$exv[3]))/$exv[3];
 $chv[4]=(($obs[4]-$exv[4])*($obs[4]-$exv[4]))/$exv[4];
 $chisq=$chv[1]+$chv[2]+$chv[3]+$chv[4];
### 
### PRINT INPUT DATA.
 print qq|\n <hr><b>INPUT DATA</b>(exp. value): |;
 print qq|\n <br> __________________________ |;
 print qq|\n <br>      <b>$obs[1]</b>($exd[1])|;
 print qq|\n \|      <b>$obs[2]</b>($exd[2])|;
 print qq|\n <br> __________________________ |;
 print qq|\n <br>      <b>$obs[3]</b>($exd[3])|;
 print qq|\n \|      <b>$obs[4]</b>($exd[4])|;
 print qq|\n <br> __________________________ |;
### 
### PRINT OUTPUT VALUES: CHISQUARE, TOKENSWAP.
 print qq|\n<hr><b>CHISQUARE:</b> $chisq, 1 d.f. |;
 print qq|\n<br><b>TOKENSWAP, p: </b>$tknswd |;
### 
### REPEAT TOKEN SWAP TEST.
 print qq|\n<hr> To repeat the <b> TOKEN SWAP TEST, </b> enter |;
 print qq|\n the revised cell totals in the four cell-boxes |;
 print qq|\n of the contingency table. Then click |;
 print qq|\n on the <b> SUBMIT </b> button: |;
 print qq|\n<form method="get" |;
 print qq|\n action="http://www.netautopsy.org/cgi-bin/toknswap.cgi"> |;
 print qq|\n<br> __________________________ |;
 print qq|\n<br>       |;
 print qq|\n<input type="text" name="aaaa" size=4 maxlength=4 value=$obs[1]>|;
 print qq|\n       |;
 print qq|\n<input type="text" name="bbbb" size=4 maxlength=4 value=$obs[2]>|;
 print qq|\n<br> __________________________ |;
 print qq|\n<br>       |;
 print qq|\n<input type="text" name="cccc" size=4 maxlength=4 value=$obs[3]>|;
 print qq|\n       |;
 print qq|\n<input type="text" name="dddd" size=4 maxlength=4 value=$obs[4]>|;
 print qq|\n<br> __________________________ |;
 print qq|\n<br><br><input type="submit" value="SUBMIT"><br></form> |;
### 
### END JOB.
 print qq| <br></body></html><br><br> \n\n\n\n |; exit;



Last Updated: December 21, 2006, by G. William Moore, MD, PhD.