<?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/poolse</title><revhistory><revision><revnumber>19</revnumber><date>2014-07-25 11:10:50</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>18</revnumber><date>2013-10-29 14:34:28</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>17</revnumber><date>2013-10-29 14:33:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>16</revnumber><date>2013-03-08 10:17:15</date><authorinitials>localhost</authorinitials><revremark>converted to 1.6 markup</revremark></revision><revision><revnumber>15</revnumber><date>2007-04-26 16:27:37</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>14</revnumber><date>2007-04-26 16:23:55</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>13</revnumber><date>2007-04-26 16:23:10</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>12</revnumber><date>2007-04-26 16:22:15</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>11</revnumber><date>2007-04-26 16:20:12</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>10</revnumber><date>2007-04-26 16:18:32</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>9</revnumber><date>2007-04-26 16:16:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>8</revnumber><date>2007-04-26 16:12:48</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>7</revnumber><date>2007-04-26 16:09:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>6</revnumber><date>2007-04-26 09:35:25</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>5</revnumber><date>2007-04-26 09:34:13</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>4</revnumber><date>2007-04-26 09:32:50</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>3</revnumber><date>2007-04-26 09:32:24</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>2</revnumber><date>2007-04-26 09:30:36</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>1</revnumber><date>2007-04-26 09:29:17</date><authorinitials>PeterWatson</authorinitials></revision></revhistory></articleinfo><section><title>How do I obtain a pooled mean standard error?</title><para>Suppose we wish to pool over each of K people (or groups) with the k-th individual having variance V(k) and mean m(k) based on a sample of size n(k). </para><para>Then pooling the K variances we have </para><para>Pooled Variance V =  [sum k to K (n(k)-1) V(k)] / [sum_k to K (n(k) -1)] </para><para>and we can use this pooled variance to obtain the standard error of the mean since </para><para>Pooled Mean Standard Error =  Sqrt{ [V] / [sum_k to K n(k) ] } </para></section></article>