<xs:complexType xmlns:xs="http://www.w3.org/2001/XMLSchema" name="PPD_PQ">
      <xs:annotation>
         <xs:appinfo>
            <diff>PPD_PQ</diff>
         </xs:appinfo>
      </xs:annotation>
      <xs:complexContent>
         <xs:extension base="PQ">
            <xs:sequence>
               <xs:element maxOccurs="1" minOccurs="0" name="standardDeviation" type="PQ">
                  <xs:annotation>
                     <xs:documentation>
                        The primary measure of variance/uncertainty of the
                        value (the square root of the sum of the squares of
                        the differences between all data points and the mean).
                        The standard deviation is used to normalize the data
                        for computing the distribution function. Applications
                        that cannot deal with probability distributions can
                        still get an idea about the confidence level by looking
                        at the standard deviation.
                     </xs:documentation>
                  </xs:annotation>
               </xs:element>
            </xs:sequence>
            <xs:attribute name="distributionType" type="ProbabilityDistributionType" use="optional">
               <xs:annotation>
                  <xs:documentation>
                     A code specifying the type of probability distribution.
                     Possible values are as shown in the attached table.
                     The NULL value (unknown) for the type code indicates
                     that the probability distribution type is unknown. In
                     that case, the standard deviation has the meaning of an
                     informal guess.
                  </xs:documentation>
               </xs:annotation>
            </xs:attribute>
         </xs:extension>
      </xs:complexContent>
   </xs:complexType>