SELECT TOP 14 ContactAssociate
FROM tb_Contact
WHERE tb_Contact.ContactAssociate = 'David'
ORDER BY NEWID()

UPDATE tb_Contact
SET ContactAssociate = 'Peter'
IN
(
SELECT TOP 14 ContactAssociate
FROM tb_Contact
WHERE tb_Contact.ContactAssociate = 'David'
ORDER BY NEWID()
)

UPDATE tb_Contact
SET ContactAssociate = 'Peter'
where PK_Of_tb_Contact
IN
(
SELECT TOP 14 PK_Of_tb_Contact
FROM tb_Contact
WHERE tb_Contact.ContactAssociate = 'David'
ORDER BY NEWID()
)

UPDATE c
SET ContactAssociate = 'Peter'
FROM tb_Contact c
INNER JOIN (
  SELECT TOP 14 ContactAssociate FROM tb_Contact
  WHERE tb_Contact.ContactAssociate = 'David'
) q ON c.ContactAssociate = q.ContactAssociate

SELECT c.*
FROM tb_Contact c
INNER JOIN (
  SELECT TOP 14 ContactAssociate FROM tb_Contact
  WHERE tb_Contact.ContactAssociate = 'David'
) q ON c.ContactAssociate = q.ContactAssociate

DECLARE @sample int
SET @sample = 7

UPDATE tb_Contact
SET ContactAssociate = 'Peter'
where PK_Of_tb_Contact
IN
(
SELECT TOP (@sample) PERCENT PK_Of_tb_Contact
FROM tb_Contact
WHERE tb_Contact.ContactAssociate = 'David'
ORDER BY NEWID()
)