how do i make my xml and xsd valid? it's still having error even though i associated a schema

Question

is my xsd correct to be validated for my xml? another problem is that even though i linked my schema with my xml, my declared element "ElectionResultsByPercentage" is still cannot be identified, i don't know why.

this is my code for xml:

<?xml version="1.0" encoding="utf-8"?>
<ElectionResultsByPercentage xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation ="schema.xsd">
  <Candidate name="John">61</Candidate> 
  <Candidate name="Sara">24</Candidate> 
  <Candidate name="Bill">15</Candidate>
</ElectionResultsByPercentage>

and my code in xsd is:

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns="https://www.w3.org/2001/XMLSchema"
  xmlns:xs="http://www.w3.org/2001/XMLSchema-instance"
  elementFormDefault="qualified"
  attributeFormDefault="unqualified"
  xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning"
  vc:minVersion="1.1">
  <xs:element name="ElectionResultsByPercentage">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Candidate" maxOccurs="unbounded" minOccurs="0">
          <xs:complexType>
            <xs:simpleContent>
              <xs:extension base="xs:byte">  
                <xs:attribute type="xs:string" name="name" use="optional"/>
              </xs:extension>
            </xs:simpleContent>
          </xs:complexType>
        </xs:element>
        <xs:assert test="sum(Candidate)=100"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

i'd also like to know if my usage of assert is correct.

if my xsd is wrong, how can i correct this because it appears to be valid when being validated in oXygen ide