<?xml version="1.0" encoding="utf-8"?><!DOCTYPE article  PUBLIC '-//OASIS//DTD DocBook XML V4.4//EN'  'http://www.docbook.org/xml/4.4/docbookx.dtd'><article><articleinfo><title>FAQ/tetra</title><revhistory><revision><revnumber>26</revnumber><date>2013-03-08 10:17:18</date><authorinitials>localhost</authorinitials><revremark>converted to 1.6 markup</revremark></revision><revision><revnumber>25</revnumber><date>2009-06-29 10:56:42</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>24</revnumber><date>2009-06-29 10:53:45</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>23</revnumber><date>2009-06-29 10:53:30</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>22</revnumber><date>2009-06-29 10:53:18</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>21</revnumber><date>2009-06-26 15:22:55</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>20</revnumber><date>2009-06-26 15:19:02</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>19</revnumber><date>2009-06-26 14:38:50</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>18</revnumber><date>2009-06-26 14:37:21</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>17</revnumber><date>2009-06-26 14:37:13</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>16</revnumber><date>2009-06-26 13:52:02</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>15</revnumber><date>2009-06-26 13:38:42</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>14</revnumber><date>2009-06-26 13:38:30</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>13</revnumber><date>2009-06-26 13:13:18</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>12</revnumber><date>2009-06-26 13:11:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>11</revnumber><date>2009-06-26 12:50:57</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>10</revnumber><date>2009-06-26 12:38:50</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>9</revnumber><date>2009-06-26 12:30:00</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>8</revnumber><date>2009-06-26 12:22:19</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>7</revnumber><date>2009-06-26 12:16:48</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>6</revnumber><date>2009-06-26 12:12:19</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>5</revnumber><date>2009-06-26 12:12:03</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>4</revnumber><date>2009-06-26 11:43:35</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>3</revnumber><date>2009-06-26 11:36:14</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>2</revnumber><date>2009-06-26 11:35:50</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>1</revnumber><date>2009-06-26 11:30:55</date><authorinitials>PeterWatson</authorinitials></revision></revhistory></articleinfo><section><title>Tetrachoric computation using EXCEL spreadsheet</title><para>The program in this <ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/tetra/statswiki/FAQ/tetra?action=AttachFile&amp;do=get&amp;target=tetra.xls">spreadsheet</ulink> will handle upto 15 dichotomous variables on upto 800 cases with missing responses assumed to be coded as blanks and the lowest valued response assumed to be coded as a '1'. The data is entered in sheet 1 and the output is a tetrachoric correlation matrix in sheet 2. Ths matrix may be copied over and entered into a SPSS spreadsheet as input to a factor analysis as described <ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/tetra/statswiki/FAQ/polychoric#">here.</ulink> </para></section></article>